willysmjeeps.com

M38 Parts book picture shows part number for the steering shaft as 7412578.
For the shaft with the knobs on it, (I think that is what is called the sector shaft) the part number is WO-804534.

M38A1 Parts book picture shows the steering shaft as an assembly, part number 8329730.
For the shaft with the knobs on it, the part number is 8677533.

My question is, will these parts enter change from the M38 to the M38A1 and vice versa?

The ratios are different so the worm and sectors would be different. The M38 had an early lighter weight gear box housing and then a heaveier housing with the water proof mast jacket that added seals at the box to jacket area. The M38A1 looks very similar to the late M38 box but the ratios are different.

I would assume an interchange is possible late M38 to M38A1 if you kept the sector and worm matched up.