Sell that 383 block and buy another good 400 block, especially with any power adder
I would hate to hear that you ran over the crankshaft at speeds
Make sure and have all the blocks you use sonic tested before deciding on how much power your going to build for.
Anything above 600 HP on pump gas you should replace the stock main caps with after market Ductile Iron(my first choice,) or aluminum with ARP main studs