Yes and no. I am not knocking either. But as example, the Automatic to block kit for Big block has 2 7/16-14 2" long bolts. An original car had 1 2" and 1 13/4" long. Look at the ears on the block, one is thinner by 1/4". Does this matter mechanically hell no. But if you are shooting for truly OEM correct. Additionally they seem to only carry one head marking. There seems to be differences depending on year what the markings would be.

I have box of original bolts but all mixed by diameter of bolt. None of the head marks or length fully match AMK kit for bellhouse 4 spd Big Block.

So yes I would like to see some known originals for a 68-70 cast bell housing.

It is complicated because many of these 3/8" bolts are similar to intake and exhaust manifold bolts both Mopar and other like GM/Ford. Nobody really cared in the 70/80 about any of this.

If you look at the bh and block. Mount surface is 9/16" at top, 15/16 for long bolt. Depth of hole in block is 1 1/16". There are machinist formulas for thread engagement in cast iron. Some of those kit bolts seem to be short some what. Would it really matter, no unless you over torqued a bolt.

I am just interest in seeing original bolts. Are they M, TR, H, Triangle? What length.