If your gonna go all motor (Stroker) i would go ahead and Purchase the 18 degree set up...saw a many 18 dergee 434ci (HIGH WINDING STUFF) turning 9,000rpm that would get it done.....it may be a little more up front fore the 18 degree stuff but for the performance difference it will be worth it in the long haul...
if you build the right 18 degree 421/434...you gonna be very surprised how it runs compared to the 350ci
Good luck
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "