OKAY - got the story, talked to the previous owner who had the car for 20 years before the current owner of 10 years bought it (Uncle sold to nephew). The engine was rebuilt but he swears it's the original block. The numbers on the block are attached on the pics, the block is stamped as a correct for '70 on the back by the bell housing with 3970010. It also has the 12-bolt (70 only), 8k tach, LCA blocks on the bumpers, and being a NORWOOD car it has the Z28 called out on the cowl tag.

The 3970010 actually doesn't mean very much. That was a block they used in both 2 bolt and 4 bolt configurations from 1969 through I think the early 80's in both cars and trucks. There were probably more small blocks with this casting number than any other.
The ACRE 10232 is pretty much meaningless in terms of factory stamps as far as I know. Probably an engine shop stamp. The cut marks on the pad are definitely wrong too. The factory broached the head surfaces on the block and the marks left from the broaching process look totally different.

There is a casting date code at the rear of the block on drivers side top near the bellhousing. It will be of the form LETTER-THREEDIGITS where the letter is the month and the next 2 digits are the day of the month and the last digit is the year. Post those and we can at least decipher the time when the block was cast. The casting date should precede the cars TT build date by as little a 1 to as much as 4 or 5 weeks generally. As an example, my car has a 04B TT date and the block was cast C230 or March 23rd, 1970.

There is VIN number stamped near the oil filter on the block by the bellhousing. It is very hard to see as its on the rough casting, especially while its in the car. This would be the gold standard to tell if the engine is original to the car. I had to photograph mine from various angles with both a flash and no flash with my iPhone to make out the letters. You may need to take some lacquer thinner to remove the paint. Don't use a wire brush!

Still sounds like a nice car. Can you post more photos? The TT indicates a deluxe black comfortweave (712) interior.

You can guess all you want.
Or you can get a good picture of the engine pad without paint and know......

I agree a clean pad will help. What I initially see is possible rebuilders stampings. Head markings look like 186 heads.

Are the LCA blocks under the bumpers a Z28 only thing?

Yes, they are a Z28 only, due to the fact they had15 inch tires.

A few more pics

Small observation, but knowledge is good. The 70 dash does not have the seat belt warning light. That, and the valve covers are on the wrong sides.
Buddy

Dash mounted Fasten seat belt light was on the 1972-1981 Camaro.

I knew about the dash (noticed that today), didn't know about the valve covers - thanks! Love learning new stuff - it keeps me honest!