I am working on getting the car now. I hope for a 68 Dart 270 more door, but I will be OK with a 70-74 Dart Custom more door. Running or not, as long as it's a solid foundation for a good build and is not wrecked. Running preferred, though. I'd like to drive it during the week and wrench on it on the weekends.
It's an ambitious set of goals. Wrenching regularly on a DD has its pitfalls, such as when the car is needed for service but not available due to parts/tools/labor. Recommend keeping a dependable beater around until all reliability issues are resolved and upgrades that are going to have the car non-op are installed and working properly.
- There's no magic needed for a good machine shop to put in hardened valve seats. No need to limit head selection.
- Before I'd go to the Offy w/2v plate, I prefer the factory Super 6 or the M1 (pn /P4529115). I'm not showing current production on either but there are several on eBag at any given time. AussieSpeed makes a beautiful 2v and 4v manifold. They are a bit pricey, sadly.
- Your exhaust pipe plan looks good on paper, not so well in real life. As exhaust gas cools it contracts. If exhaust gas velocity is enhanced, as in scavenging headers, it allows the engine to breathe better. The best way to maintain or improve exhaust gas velocity would be to have the tube constrict rather than expand (expecially for 4-stroke engines. Suggest you run the exhaust 2.25 all the way.
- Good move. Recommend the R/V kit. IMO the next level up is harsher than it needs to be for mainly street use.
- The 7.25 is adequate for a street /6. Beware all 7.25s are not equal. The LBP 7¼ has longer axle tubes and different off set to the backing plates. The LBP 7¼ is found on disk brake 73 - 76 A-bodies. That said, I have not seen a SBP 8¼. If you go that route, remember to get the saddles and clips, too. The 8¼ has a 3" diameter tube, where the 7¼ has a 2.75" tube.
Good handling improvements with this. Recommend you get the LCA along with all the hardware. Major change in bar (and K-member) beginning with MY73. It is a largely futile exercise to try to put the later bar in the earlier K-frame or vice versa. Note: If you have (for example) a 72 body, A 73 k-frame bolts right in. While your car is being aligned, you can get aggressive with + caster. Do a search for SKOSH chart on FABO.
??? Disk/Drum is possible with SBP or LBP. Besides the brakes, recommend the proportioning valve and a dual well master cylinder. Only the 65 & 66 A-bodies with disk brakes had single well master cylinders.
With the 73 or later K-frame, the M/J body cop car boxes can be used.
The widest 14" Mopar-made SBP wheels were 5½ wide. Anything wider has to come from the aftermarket. Which leads to the attraction of converting to LBP axles. I had 15X7 Magnum 500s (4¼ backspacing) on a 73 Custom mounted with 205/60-15 tires. No hiccups or bumps with install or operation. My 72 Demon has 15X7 cop car wheels (same bs). Fit is tight, ft fenders installed "wide". At full jounce/compression, the tires bounce off the rear inner fender and the front fender lip when being turned. No problems under normal situations. Note: Conversion from drum brakes to LBP single piston (factory) widens the front track by a little over an inch.