painless transmission swap?

[Adams74Chevy]

Since the weather seems to be becoming spring like I am looking to tear into parting out the '87 V20 farm truck to get it out of the way.

My '73 K20 currently has a very leaky TH350 with a NP203 that has a 2wd conversion done previous to me.

So my thought is take the fairly recent rebuilt TH350 and the NP208 out of the '87 V20 and put them in the '73 K20.
Obviously the bell housings should be the same bolt pattern...but are the splines different on the NP208 vs the NP203, is there any electronics/computer on the '87 TH350 I'll have to deal with differently than the '73 TH350. The splines shouldn't be an issue the driveshafts of the both trucks are good and both are regular cab long beds.

I'm just trying to make sure my ducks are in a row before it tear in and find a surprise I didn't expect.

Thanks,
Adam