Every Member here know's I will jump on this thread:
I doubt if you will find a 70Z LT1 motor, at least one intact, as there were only 8,733 built for ½ a year in 70; however, you can build a similar motor from an 010 4 bolt block casting, 69 or 70 Turbo-Fuelie heads but recommend either AFR or Vortec, Edlebrock RPM with a 750 Holley Dp and run a similar profile cam. 350 OEM Forged Cranks are not impossible to find. New Eagle SIR or Scat rods and Forged Pistons from JE or Speed Pro.
The 11:1 Static Compression of the 70 LT1 is not suitable for to days pump gas and not high enough for E85. You can either it down to around 10:1 for gas or up it to say 13:1 and run E85. I personally would go the E85 route as you can extract considerably more power out of 105 E-Octane then 93 Octane Pump Gas and the motor will run super clean both inside and outside plus will pass environmental emissions. Suggest you read this: http://www.raceone85.com/
. Running any where between a 11 to 12:1 Static compression on the street is a Dead Zone (a Do Do Bird) with to days fuels unless you want to pay out for racing gas or put additives in the tank. The 350 LT1 delivers considerable more Hp & Torque at lower rpm then the 302 and behaves nicely in everyday traffic.
Yes you can bleed off Compression with a Cam selection but then you have NO Torque and your engine had better be designed to take the stress of Hi-RPM's - Thus NO Solution.
Keep in mind that you can buy Stroker Kits for the SBC and build yourself a 383 or a 402 and even a 427 CI SB Engine.
For a Cam I would suggest updating to a Hydraulic Roller Retro-Fit but if you want that extra Hi-RPM you require either a Solid FT (CHEAP) or SR-Retro-Fit (Expensive). Note that running FT engines today is precarious as you have to be wary of the ZDDP Oil content.
A Donovan Cam Gear Drive or a Summit Belt Cam Gear drive on top of a Jessel or the cheaper Chinese RKM 350 Shaft Rocker system or a Manley Valves topped with a Jomar Girdle would be nice but then again more bucks - LOL
If you find a 70Z LT1 motor contact me ;o)