One thing to keep in mind is your adding 60 cid.,and I have seen a difference of 100 ft lbs of torgue @ 3000 rpm..

As an example my 500" 440 makes 600 ft lbs from 3300 up, what this means for me was my converter that stalled at 4500 with a 520 hp 545 tq 446", the 645 hp 620 tq 500" stalled it at 6000!!

Both motors run the same rpm range but the big motor mph better so it needs a different gear also.

I'm just saying there are more parts to get after the new bulit.