If I were you I would look for a late 53 or 54 235 to drop in your 48,the 216s had a splash oil system and finding anyone who knows anything about them might be hard. It will bolt right in to the original trans and look original if thats what you are wanting,the 55 to 62 235s and 261s will bolt in but they require a shortened waterpump and the waterpump sits lower in the block so a stock fan might be difficult. The 235s had a full pressure oiling system like the modern motors unlike the 216 that had a slash system with poured rod bearings and dippers. Jeff