Biggest bang would be the Oregon cams 2106 (easy), Dutra RV10RDP (hard if Doug lost his stock in the fire) and the Dutra duals with the pipes run back at least behind the transmission cross member before the collector back into one pipe (much harder). Easier if willing to go to a mini starter but I am on a mission to make this work. /QUOTE]
Hmmmm....looks like your heat shield is going to get HOT because it's bolted to your exhaust. I'd look into making a bracket/shield off the starter or a wrap.
If you're hanging onto the large starter because of the classic Mopar sound....I'm as traditional as anybody but I went with a Denso mini. Never really miss the sound and it's half the weight, smaller, and spins the engine faster so it cranks for a shorter time and I never notice.