Assuming they're in decent enough shape where a fresh valve job will revive them (no cracks or broken pieces), the 302 heads are great to run on any small block (273, 318, 340 & 360).
302 heads are always a good option. If you run a bottoming tap into each head bolt thread in the bolt and blow the holes out with compressed air (should always do this with all blind screw threads), the longer bolts will work fine assuming they came with washers.
Nothing wrong with using an auxillary gauge to verify there's nothing wrong with his 426 Hemi. It's sounds like we have the same idea @moparleo perhaps I didn't provide enough description. I didn't mean gauges for his dash, but under the hood to trouble shoot. I have in my arsenal, auxillary oil...
Alternator discharging slightly at idle is common for our Mopars. I agree the 5 volt regulator could be (or has) going bad. Buy some inexpensive oil and water temp gauges to connect temporarily. That will help confirm all is good with the engine and the voltage regulator is the culprit. 426 Hemi...
@heminut about how many hours do you figure for the modifications (paint removal and Dremel out the lip)? So people know what they're getting into. Certainly looks very nice! Great job!
I listed Challenger first as he stated quarter panel. Then listed the Barracuda/Cuda for our Plymouth friends. If your original holes are trashed, go the route @Adam went. And yes, there should be a thin foam gasket in there.
If you got the original dash and treated it with some good vinyl protectant (303 Aerospace, STP, etc), it might be your best bet. Wouldn't have to wait to have one made and you'll make your car show date.
I believe Year One sales both plastic and steel core dash pads. In the original is in really mint condition, I'd go that route if it was me. But a steel core from Year One would be a great choice too.
None of us is perfect, but as a group, we're pretty dang close.
As a side note, I've not run the positioners or anti-rattle clips on my 70 Challenger since the early 90s. I noticed my 98 Dakota has pin type calipers and neither of these parts. Correct for a "show" car, not needed for a "go" car. 🙂
Is it the intake and throttle body fuel injection causing the filter assembly to be too high?
A Holley Street Dominator single plan is close to factory stock height. It's an ugly intake, but doesn't really give up much horsepower or torque across the rpm range. Kind of an amazing intake after...