Be a neat thing to develop a cast aluminum pan for these. I've got a Chevy II car 153 my Dad put in our CJ5 many years ago and I'm replacing it with 120hp Mercruiser 153. The car 153 had water in the oil and oil in the water, so I'm curious if it has a bad head gasket or a crack somewhere. Had to swap pans and oil pickups. Got a new repro exhaust manifold from Rock Auto. The original exhaust manifold was corroded and had small cracks. I've got another core 153 car engine and and another 153 Mercruiser with a hairline crack in the block. Also have a bare 153 block, so plenty of extra parts to built another one if the Mercruiser I'm installing doesn't work out. I noticed some small differences in the 153 passenger car head and the 153 120hp Mercruiser head.....the center exhaust ports are cast slightly different as they exit, but perfectly compatible with the car manifold.