Your 302cid/290hp Z28 engine block is on eBay...
Engine pad is stamped: 18N469697 V0708MO
Block casting number: 3914678
Full VIN: 124378N469697
Seller id: lebeau4parts
Seller location: Rogue River, OR
http://www.ebay.com/itm/291771069888?item=291771069888&viewitem=&vxp=mtrSeller description...
"1968 MO 302 CHEVY Z28 BLOCK, THIS IS THE REAL DEAL. STANDARD BORE. ONLY ONE PROBLEM, IT HAD 3 CRACKED MAIN BOLT HOLES ON THE MAIN WEBS. I THINK IT COULD BE FIXED WITH HELI COILS AND MAIN STUDS AND HAVE ZERO ISSUES WITH IT. I HAVE BEEN KEEPING THIS BLOCK FOR OVER 15 YEARS BECAUSE ITS A REAL ENGINE. STAMP PAD READS V0708MO SERIAL NUMBER OF THE CAMARO IS 18N469697. IF THIS IS YOUR Z I HAVE YOUR ORIGINAL BLOCK. THIS IS FOR THE BLOCK ONLY. CAN BUILD AND DYNO FOR EXTRA. PLEASE ASK ANY QUESTIONS. THANKS"Paul