[FWDLK] Early Hemi? Early Poly?

Because of my deprevity from early Chrysler engines, I came across an OHV motor less heads and intake at a junk yard this weekend. I could almost swear it was Chrylser (very cursty with gunk, so hard to get some numbers). It had the round pattern where the bellhousing bolted, and it had a moparesque oil pan. It was center sump and looked like a big block pan except in the (I think) front it tapered in on each side a little. It had an aluminum water pump on the front, a spin on oil filter, and a TRIANGULAR flex plate (6 bolt crank). The pistons were high compresson bu tthe valve releifs were on the same side (they looked like wedge pistons). Distributor location was in the back. Thre was a casting number on the bellhousing flange, behind the distributor hole. It started with 13 or 18, but and the whole thing smelled of chrysler, but what on earth is it?

My best guess is that it was one of those motors that became a hemi when you put the right heads on it, of which i know so little. I'm also guessing that the water pump and oil filter adapter were aftermarket jobs. Any enlightenment would be appreciated. Thanks.