"So far i've sourced and 250 and th350 from a 77 camaro"
I thought you Brits like to go through the gears manually. Get a clear idea of what you want before you start taking it apart and gathering parts.
Many trucks are "exploded" by owners in with the goal of making a daily driver. Think it through before you start.
I have a 1940 gmc 3/4 ton. My gmc has the same steering box and front axle as your 38. I chose to get a dropped axle from a 41-54 from Sid, and install 6 lug 12 inch disc brakes on that axle. It is a virtual bolt in upgrade. I also used a steering box from a 41-46.
Here in the states, parts are more available for these old trucks. Out in the UK, I would use what is available... ie Jaguar clip, engine and rear, but I would strongly consider restoring it to stock specs.
