78 F100 tranny questions

I just dealt for a nice little '78 F100 SWB Fleetside. It was a 302 4spd truck, and the 4spd is still there minus shifter. I also got a 80k mile '76 300 6 and a (i think)C4 auto.(looks too small to be a C6). the motor turns free, and the tranny goes in and out of gear fine, but both have sat and not ran for several years. I know i want to run the 6cyl, but im not sure about what trans...the 4spd was makin some funky whining/growling noises before they unmotored the truck, and the shift rails seem worn...the C4 hasnt been run, and all i really know about it is that the shift lever on the trans moves freely. what do you guys think i should do for a trans?? rebuild the 4spd? or rebuild the auto? im certain i know where there is a flywheel for the 6 and a clutch shouldnt be a big deal. if i get the auto i have to come up with an auto column, or put a floor shifter over the hole for the manual shifter.
what to do, what to do.
btw this truck will be daily driven.
later

[addsig]