New to me 71 GMC, a few questions

[Christiansok]

I've been lurking these forums for awhile but just last sunday I bought a 71 GMC for my daily driver and it has a few quirks that I hope the experts here can help me straighten out.

First off some details:

1971 GMC 4x4 LWB
350ci V8, TH350
3-4"? home made body lift
31x10.5" tires

First thing to raise some questions was the VIN. It starts with a 'C' but the truck is 4 wheel drive. So I assume a previous owner swapped a cab off a 2 wheel drive. The thing I couldn't figure out though, in the digit where the year usually is it has '-' instead of any number 7, 8, 9, 0, 1 or 2.

The second thing that I'm unsure of is the tranny dipstick. The stick is brand new but when I checked the fluid level after driving it 2 hours home (with no problems) there isn't a drop of fluid on it. The stick is about 34.25" long and from eyeballing the tube I think its too short. How long should it be?

Third, are the front leaf springs on the 4x4 models originally flat? I was expecting them to have some upward arch but mine have a slight downward arch. I was wondering if they were flat originally and sagged down over time.

Fourth, my fuel gauge always reads empty. Is the wire running to the sending unit on the tank the ground or power? I cleaned up the wire/connection on the outside thinking it was the ground. Unplugging this wire from the fuse panel under the dash buried the needle on the fuel gauge so the gauge itself works. What is my next step? I'm thinking either the float doesn't float inside the tank or there's a short in the ground. Where is the ground for the sending unit located?

Lastly with the body lift in place the mechanical fan doesn't line up very well with the radiator causing it to run hot idling. I've read a few electric fan swaps (jeep fans, lincoln fans, etc) but has anyone used the 16" electric fan kit from LMC (or a similar all inclusive kit)? I've never done an electric fan upgrade so I was thinking a kit would be the best way to go so there's less chance of me screwing it up.

Also, are there any small upgrades I should consider that are done to these style trucks by expierenced people? What I mean are upgrades specific to this style truck that among people familiar with them are pretty much common knowledge (i.e. something about getting a 4-4.5" tall air filter?).

Anywho...appreciate any help/experience you guys can share.