The 235 babbit beater was last used in '53 sedans with 3-speed. '53 sedans with PG got the full-pressure 235s. '54 was the first year for all full-pressure 235s, and the last year for 6 volt and exclusive use of 6s in Chevys.
You can have your babbit beater reworked for the aftermarket-style insert rods, & do other upgrades like adding a bolt to the crank pulley. However, you must find a shop that has done it before, if you have it done locally. The machining work that has to be done is specialized, and most local shops will butcher the work unless there is an old hand around who's done it before.
The easiest way to upgrade these cars is to use a full-pressure 235 made from '55-62. Using the custom motor mounts and short shaft water pump, the later engine will drop right in, with no modifications to the car. I just replaced my '54 full pressure 235 with a '60 235, and everything clears. You just have to look at the later 235s before buying, as some '55-57 blocks had the side mounts you'd need, and some don't. Most '58-62 engines have the triangle-style bosses you'd need. You can re-use your bellhousing, starter, flywheel, tranny, linkages, etc. You'd need the engine and manifolds to do the swap. Look in the paper or scour local junkyards, as these engines still turn up regularly, if you look for them.
good luck
chip
