I have an LM7 (5.3) short block, and have a set of 799 casting LS6 heads, and an LS6 intake/throttle body.
I also have a set of beehive springs that are going on the heads that can handle .600 lift.

Will I need to use the 9.5" LM7 (862 casting) pushrods, or get a set of LS6 10.5" pushrods?

Also, to keep my compression up, will I need to mill the heads, and how much?

Last question for now, what cam would work nice to put some power down for this setup? I love the Thumpr cam sound, and want a meaty idle sound, but don't want it to be a dog off the line either.

Thanks for your help!
Additional info - this is going in my 73 Corvette that currently has a stock stall (1700), TH400, and 3.08 gears.

 

Where did you get the 9.5"/10.5" dimensions for pushrods? They're all approximately 7.40", except for the LS7.

The 799 heads have chambers at about 64cc while the 862/706 castings are at about 61cc, so you have about a 3cc difference to make for. That's approximately .018" that needs to be milled off.

After you decide how much to mill, then I would suggest measuring for pushrods, but I'm sure even 7.40" will work fine.

 

Well, guess I read some bad info. I will get the heads milled.

Anyone have a recommendation on a cam?
Should I also switch to the 4.8 pistons while it is apart?