would like to increase power of 69 z28 with stock dz 302. would consider building bigger short block and using stock heads and cam . need to preserve stock appearance and pick up a lot more torque and hp

 

Easiest easiest cheapest way is to put a 350 crank 3.48 stroke and pistons your current Pistons are floating pin you can use the rods with the 350 Pistons if you get pistons set up for floating pin and you'll have a 350 motor. both 302 and 350 are 4 inch bore

 

I think I would pull that rare engine out and store it. Build a different one to beat on.
Chris

 

Exactly start with a roller cam 350 block and build a 383 with heads that run perimeter bolt valve covers. Dress it up to look like the DZ-302. The casual on-looker will never know the difference.

I built the same setup for a L-82 Vette a few years ago and used valve cover adapters on the Vortec heads. Sure it had the Vortec intake pattern but 99% of Chevy guys never even noticed.

 

Would be interesting if it was related to the 3rd gen f-body platform.

But, it isn't.