I need to get another block for my 6.5 application. I have a block which is a 6.2 with casting number 4023660. Will that work? How much do I have to bore .078? Thanks.

don't bother boring just put your 6.5 parts on it and run it as long as the main cap registers in the block are not cracked, check the sides of all the outer bolt holes of the 3 center main registers, i had a hard time finding one with no cracks, one was cracked so bad the crack went around the back side of the crank(only 80,000 miles on that 660 block)

Thanks for that response, outofline. Just wondering, wouldn't that reduce my horsepower and lower the compression? Furthermore, that 6.2 block needs to be bored so instead of going 30 over with new pistons, why not use my 78 over that I already have? The machinist said no extra charge for going to bigger bores.

i would only bore an engine enough to clean it up, leaves extra strength and allows for clean-up if needed later. i don't think you'll lose any power from that reduction in C.I.

.030 is max overbore. Any more than that leaves the cylinder walls too thin. Your machinist isn't familiar with 6.2s and 6.5s if he would suggest that.

Thanks for that response, outofline. Just wondering, wouldn't that reduce my horsepower and lower the compression? Furthermore, that 6.2 block needs to be bored so instead of going 30 over with new pistons, why not use my 78 over that I already have? The machinist said no extra charge for going to bigger bores.

heaths land speed truck is a 6.2 599 block with 6.5 heads, you would not notice the difference between the 6.5 and the 6.2, a few guys have used the 6.2 short block as the 599 block is the preferred replacement vs the newest 6.5 506 block

Ok, thanks for the help to making a decision.