The 153 is essentially 2/3 of a 230 inch 6 cylinder. It shares a lot of the internal parts with the 230 / 250 such as bearings, timing gears, oil pump, con rods. The bore is same as a 230 so whatever works for pistons in a 230 works in the 153. Valve gear is the same as the 6's except for obviously the camshaft. Externally it uses the same timing cover, water pump, thermostat neck and housing and all that, and on the back end it uses the same flywheels, starters, bellhousings, etc as the 230 / 250 and the internally balanced small block V8 Chevys. The little 4 banger is a lot happier with the smaller diameter flywheel and 10.4 inch clutch assembly than with the larger flywheel.
The engine was used well into recent years as a marine version ofered by Mercruiser so rebuild parts are available that way as well as through automotive sources. A 181 inch marine version is out there too and for a couple of years they came with an 8 port head and around 10 to 1 compression. The 8 port head is not a good flow and there is very little room to do a port job without ruining the head.
A marina will no doubt be more expensinve to buy from but if that is the only place you can get parts then grin and bear it.
I'm in the process of negotiating for a 153 myself for a bare bones T bucket type car I want to build. Years back I had a 153 and foolishly scrapped it in favor of engines with a few more cylinders.
