A903 - which one???

Rainy Day Auto said
is it aluminum or cast iron

is it a top loader or side loader

The 903 is aluminum

the 745 is a top loader

The 230 is side loader that looks like a mini 4 speed

one of the first two are most likely

903 is an iron case with a flat top cover
745 looks like a 903 except the top cover has a hump in it to clear a gear on the main shaft
230 has a side cover
65 and earlier transmissions have a ball and trunnion yoke

Brian