Either set up can be used but the spacing is different. The flywheel must match the starter and vise-verse. The cost of putting a new ring gear on the 258 flywheel vs resurfacing the 4.0 flywheel is kinda a wash. Do one of the two. How you wire the 4.0 should also play into the decision. If using the 4.0 distribution power block and relays would be easier with the 4.0 starter and flywheel.
1975 CJ-6 304 T15 Dana20 30/44 3.73
1983 CJ-8 258 T5 300 30/44 3.31 Looking for full or half hardtop buy or trade
1986 CJ-7 Laredo 4.6 stroker T5 300 30/44 3.31
1986 TJ-7 Trail Jeep project in the works
2003 Inca Gold TJ Rubicon