My first post on this forum! Looks like this thread is a little old but thought I would through in my 2 cents.  First, congrats on owning a 70.

I have a 70LT1 Vert and have been looking for the right parts to build the motor back to original. It is worth it to me as I am sure the car is an 70 LT1. I have probably looked into around 25 engines claimed to be an LT1 and only one of them was real and that came out of a Z28.

One thing is certain; the numbers you have listed mean this is not an LT1 engine. If it were a factory replacement block for that year it would be a CE block.

Other things you want to look for to see if it was "built to a 70 LT1", cant tell you how many times I have heard that and most aren't even close -

Before I invested money building an original LT1 I would make sure the car is an LT1. I only say that because you can build a better motor for less money as technology has changed a lot since 1970.

Real quick checks on the car that should tell you – single fuel line with no return lines, 6500 red line on the tach, should have either the transistor ignition or the three holes where it used to be on the front driver side fender well, no expansion tank on the brass/copper radiator, heavy duty U clamps holding the U joints on the half shafts. They can have several different rear ends – mine has a 4-11 so that won’t help you.

Long first post, sorry I ama little to close to this subject. Let me know if you want more info.

Steve