D100 slant build
Dutra RV10-RDP cam, that is Oregon Cams № 2106R. Inexpensive, skillfully-ground, and a terrific torquer that won't run out of breath as early as the stock cam and won't disappoint you like Comp's junk.
Ignition:
HEI upgrade with a thoughtfully-recurved distributor (get with DusterIdiot over on slantsix.org)
Stock exhaust manifold's not too bad if the heat riser valve works (all the way working) and you put a decent exhaust system in it.
Dutra Duals are better without the hassles and drawbacks of headers. Exhaust system either way: 2-1/4" pipe off the stock manifold (or 2" pipe off of each of the Dutra Duals' outlets and into
this wye connector), 2-1/4" pipe into
this muffler. It's in Walker's QuietFlow SS premium OE line, all stainless steel (which is nice for durability), made for the '01 Jeep Cherokee 4.0 so it's easily got the flow capacity for a healthy 225 and it's tuned to keep an inline-6's exhaust from droning, has a 2¼" inlet and outlet (can easily step down to a 2" tailpipe). The inlet has a 2-bolt flange meant to bolt directly to the outlet of the Jeep's catalytic converter, but there's plenty of length to the input pipe that the flange can just be sawed off in 5 seconds at the exhaust shop.
2" tailpipe with resonator. If I'm rich, I like a
Flowmaster HP2 stainless unit with 2" in and out. It's 18" long, which is a workable fit behind most A-body quarter panels. If I'm broke, I like a Walker №
17198 4" round can-type unit, 2" in and 2" out, with offset outlet next to a proper hanger bracket.
(Tailspout outlet between 45° and 90° outward, and 45° or more downward.)