Ditching th350 for sm465 questions, maybe GV OD

[greywurm]

I have a 71 long bed with a 350 sbc and th350. The trans is tired and I'd rather have a manual in the truck anyways. The low geared manuals have interested me for a while but I haven't been able to find a decent one for sale locally until recently.

Found a guy selling an sm465 with most of what I need for the swap except the high hump and clutch pedal. The 465 came out of a 72 c20.

Parts seller has listed:
Bell housing, the clutch, pressure plate, splash shields, shifter, manual transmission cross member and all the original clutch brackets and linkages.

My driving usage is: I haul loads locally for house projects (Lumber, soil, etc), and cruising locally. Due to where I live, it does see the highway some, so I think it's good that I have a 3.08 rear.

Now for the questions...

1. I have some concern with the drive shaft. The seller is helping me understand some issues I might be looking at but hoping you guys can get me a better idea. I believe the 465 is going to be shorter than the 350 and my drive shaft will be too short. If so then I need to get it to a shop to lengthen it. I'm not sure what kind of shop to Google for in my area. Trans shop or are their specialized driveshaft shops?
   
2. Also should note that I swapped the 350sbc in place of an i6 250 a few years ago, so the motor is back on the firewall sitting on the BBC mounts. Truck was originally a 350, but someone swapped in the 250 and I made the choice to keep the new motor back so I didn't have to extend the drive shaft.
   
3. Seller mentioned the 465 is a fixed yoke and mine might be a slip yoke. How do I tell from looking at it? What does it take to make sure the yokes match up?
   
4. He still has the 2 piece shaft from the c20. If I can get it for a good price or it can aleve a lot of head ache, is it worth getting as well? I don't know if I can join the input side of the c20 with my output side of my c10 or if a driveshaft shop can marry the two somehow. Or if I can just swap shafts.
   
5. Is the spline count or yokes different between the rear ends of the c10 and c20 that would make it impossible for me to swap in the c20 driveshaft? Anything that would make this a bad idea? If you can't tell, I know very little of the driveshaft or rear end.
   
6. There is also a local ad for a Gear Vendors OD with a Ford c6 adapter for sale separately. This GV unit plus additional 465 adapter is probably out of my price range right now, but I think I need to consider OD if I am going to mess with the drive shaft for trans swap, since if I decide to add it later, I'll have to mess with it again. Is the GV module the same for any trans, just needs a different adapter? I could swing the 464 and GV now, the adapter later on and just wait to do the swap until I have all the parts. Also, is there anything with the yoke that needs to be consider with GV vs just the 465?
   
7. I have read mostly positive reviews of the 465 behind a stock 350 with 3.08 rear. Is there anything anyone wants to add that is good to know? I think the GV with any trans will be night and day for the highway driving.
   

Thanks for any of your input. Project started out straightforward then is now appearing to be much more than anticipated.