From SoCal, seeking perspective on new '68 Dart aquisition

Hello & nice to meet you all.

My first post here, and it is primarily because of my new aquisition, which is a '68 Dart Sport Special notch coupe. It was a recent Craigslist find, and is a VERY COOL little father/son project that I'm taking on with my 16-yr old. It is currently stock and untouched. He is going to learn to drive in this car, and eventually own it, and so far he loves it. Currently it has a non-running 225 hillside hemi.

My point to posting is to address the direction I really ought to take with this car. It is mine since I bought it, but I am offering it to him after he turns 18, and I expect it will be his at that time. The 225 idled like it was an absolute nervous-wreck, and I found it was due to bad exhaust valves in #3 & #5. The bottom-end never knocked, or gave me reason to stop and think. It sounded fine, and I will go so far as to say it IS fine. My son & I have pulled the head, and have verified the bad valves in #3 & 5--the darned things are practically D-shaped! The head rebuild base estimate at my preferred machine shop is going to be apx. $550, minus valves & springs, but including hardened exhaust seats (I would probably go 1.70-1.44's w/340 springs).

OR, I could do a 318/904 swap with a running engine/trans, and upgrade the platform for apx. the same price!

This car is already going to get disc brakes in the front, and that rear end is coming out, with my mind centered around a Ford Exploder/Late-model Mustang disk 8.8 rear, and a driveshaft made. I already have 11.75 rotors that came in the trunk of the car, just with the wrong spindles. These will make their way on the car because the brakes will make the car safer.

The proverbial angel on my one shoulder says to rebuild the head on the 225 leaning tower of power, and take advantage of my son's enthusiasm for the teardown on this motor so far, and see it through. The engine will VERY LIKELY run like a champ after the headwork, it will get mileage over and above any v-8 I can prep, and he won't be an outright danger to society as he endeavors driving under the influence of those occasions when he was a young passenger in my '65 big block Belvedere. On that note, there are probably times he remembers that I don't!

The proverbial demon on my other shoulder taunts me with how I would like to see this car evolve, and stabs me with his damn pitchfork while boldly stating, "how can any self-respecting hot-rodder plan on expending such effort and expense on the LEAST-DESIRABLE drivetrain combination possible???!! At least, install a 318/904 and tune it to the 9's for mileage if that is a concern, and have a platform that actually increases the worth of the car. Especially, since the plan is 4 wheel disc brakes with a modified rear with a custom drive shaft if length has to be addressed!

My son doesn't read car magazines like I did when I was young, and he's more of an intellectual. He loves this project, however, and this is what it took to get him out into the garage and off PC video games! He IS going to college after high school, and I actually rue the day that likely comes when he continuously bums a $20 off me for gas--I expect there are some Dads out there that can relate...

I'm just trying to think ahead, and I'm sure there may be some of you out there who can relate, or maybe have had some well-balanced solutions to this quandary!

Again, nice to make your aquaintance, and look forward to some perspective on this.