Yes, you are right. Any 4-53 block will fit your 1950. Be aware that you may need to change direction of rotation and possible filter location if you're using a long block from a generator or etc.
As an example I am using a 4-53T in my 1900. This block is totally different internally than a natural 4-53. The exterior is 99% similar.
Before I added the 4-53T engine, my modified 2 valve head on the original engine flowed better than the previous 4 valve.