NO repro complete body parts that I know of at this tiem, especially something like a roof panel. Only good, useable salvage yard parts.
Looking at the factory "roof joints", the panel will also include a bit of the front A-pillars, the center B-pillar mounts, and part of the full rear C-pillars. Is you car an orig factory vinyl roof car where the top fabric determirated, exposing the cloth backing, which accumulated moisture and rusted the usually un-painted top panel? On a UniBody type body, the roof is a major structural unit, so replacing one takes some additional body bracing BEFORE the current roof can be cut-off and replaced. PLUS an expensive situation, too! Not like replacing a fender or hood where the part is unbolted and replaced.
For a larger engine, it would be MUCH easier and much less expensive to get a stroker 408 to replace the existing 360. TOO many different items between the LA engine family and the B/RB engine families, by observation. Yes, all were assembly line installed situations, BUT the LA engines have their own unique set of items, as does the B/RB engine family. Goes much farther than just the basic engine mounts and the transmissions the engines are hooked to.
MANY rear axle ratio choices for the Chrysler 8 3/4 rear axle, BUT check to verify that is what's under the car. The most common ones for an OEM factory installation would be 2.76 and 3.23. You can go to 3.55, too. Need to go with a complete drop-in "differential chunk" as changing ratios without the appropriate differential gears from the factory is much easier to do. Changing to something different than what you now have, with stock gears, could require a different differential case, which has a spacer with the new aftermarket ring gear set, to compensate for the thickness of the ring gear when compared to the factory set-up which needs no spacer.
In one respect, you can NOT get an older C-body to match off-line acceleration to ANY modern vehicle . . . unless you also put a modern 6-speed automatic behind the motor. Reason? The modern 6+ speed automatic have a low gear ratio of 4.50 to 4.90 in 1st gear. Compared to the 2.45 low gear ratio in the 3-speed TorqueFlites (of similar low gear ratios in GM THM400 or Ford C-6 automatics). So, you can easily be left behind by modern 4cyl turbo motor cars at the red light, by observation. Changing to a 3.55 or 3.23 will NOT fix that, either, even with a larger engine.
Exhaust kits? Check TTI for items.
Just some thoughts and observations,
CBODY67
