Beginner Road Track Racing: Feedback on Engine Options Wanted

I’d appreciate constructive feedback from those who have experience in/knowledge about road track racing on some engine options for an upcoming build. I’ve amateur drag raced since childhood and am interested in starting road racing with a dedicated track car. It will be street legal and drivable enough for 30 minutes on a highway to the track where I’ll swap out the wheels/tires, so keep that in mind. I understand many of the principles of road racing having grown up around racers and racing pavement motorcycles, but I’ve never actually beaten a vintage car on a road track and don’t know any vintage road racers for input.

I recently purchased a solid but neglected unrestored 1969 Valiant coupe for the build. It’s a factory 318 4-speed car that doesn’t run but still has the engine and transmission. I’ll weld in frame connectors, a 6-point roll bar, swap in something stronger than the 7.25” axle, etc., and it will get front and rear disc brakes and sway bars. For this thread, I’d like to focus on the engine though.

The track I intend on running has only one straightaway and a lot of turns, so top speed isn’t much of a concern compared to low and mid-range. For now, I’d be happy with 400 – 450 HP at the flywheel, although I imagine even 350 HP would still be fun as a beginner. While the short stroke and big bore of building a B-block 400 is attractive, I want to shave off as much weight as possible so want to stay with an LA build. This is also a budget build to get me into racing before determining future upgrades as I gain experience, so I’m not looking to go all-out or even close to it. A main area of uncertainly for me with road racing in mind is where the balance lies between cubic inches and RPM in that substantially more cubic inches out of an LA will take a longer stroke versus less cubic inches and a shorter stroke. I don’t know what the feel and function of the car will be with a 3.31” stroke compared to a 3.58” compared to a 4” and therefore don’t know if a 318, 340, 360, or 408 is an ideal setup for a beginner to have some fun with enough room to grow into an intermediate level of skill.

I already have a set of aluminum heads and an ED4B intake that will go on the engine, and I’ll note what I have and what I would need to buy and have machined. I'll perform oiling modifications and the like.

Option A – Least Expensive:
360 LA-Magnum Roller Engine. With the options below, I’d be comfortable maintaining 6K RPM with the thinking sustained 6,500 RPM might overstress the factory cast crank. Here are the details:

-I have a low-miles 1994 Magnum 360 engine with the rocker shaft oil galleries to use LA heads. It has clean bores with the factory hone still visible and will clean up with just a professional hone job.
-Use the factory 3.58” cast crank, no machining necessary.
-New I-beam rods with 7/16” bolts (need to buy, unless someone has experience that the factory rods/bolts will handle things)
-New flat-top LA hypereutectic pressed pin pistons to get closer to the deck (need to buy)
-Have rotating assembly balanced
-Have the block machined to zero deck
-Reuse the factory Magnum hydraulic roller lifters (I prefer solids but already have the roller lifters).
-New roller camshaft (need to buy).

Option B – More Expensive:
LA324 (overbored 318). With the options below, I’d be comfortable maintaining 7,500 RPM.

-Have the factory 1969 318 block overbored 0.040”
-Use the factory 3.31” forged crank (need to have it turned)
-New I-beam rods with 7/16” bolts (need to buy)
-New hypereutectic pressed pin pistons (need to buy)
-Have rotating assembly balanced
-Have the block machined to zero deck
-New solid flat-tappet camshaft and lifters (need to buy)

Option C – Most Expensive:
LA340 (using a polyspherical A318 block). With the options below, I’d be comfortable maintaining 8,000 RPM

-Overbore a 1966 A318 block I already have 0.090” to use 340 pistons (the walls are thick and will take it with adequate wall thickness left)
-Use the A318 or LA318 factory 3.31” forged crank (need to have it turned)
-New I-beam rods with 7/16” bolts (need to buy)
-New forged full floating pistons (need to buy)
-Have rotating assembly balanced
-Have the block machined to zero deck
-New solid flat-tappet camshaft and lifters (need to buy)

These are the three entry-level options I thought of using the parts I have on hand coupled with some parts I will need to buy. I’m open to hearing other options using the parts I already have or if the build can be done for not much more cost if I have to buy more parts. The question boils down to if a 6,000 RPM 360 roller-cam engine will get the job done well with room for me to grow, if spending a little more money on machine work to build a 7,000 RPM 318 flat-tappet cam engine will be a substantial benefit, or if going with the more expensive fully forged 8,000 RPM 340 flat-tappet cam engine is worth the extra cost. I may reach a point in skill and enjoyment where I want more power and need to build another engine, but I'm trying to avoid either spending too much up front for overkill or spending too little and not having the room to grow in skill.

I appreciate any constructive feedback those with road track experience/knowledge can give. Thanks.