Chevy Cheyenne pick-up dash lights and tail lights out.

The pick up sensor is on the drivers side of the transmission.

short in turn signal switch.

you will need to remove the dash:

http://www.ehow.com/how_5588616_remove-chevy-dashboard.html

ck the wire that comes from starter,,see if it didnt rotted off,,

could be bad headlight switch

on a panel at the side of the dash or under the dash at the emergency brake. TAIL LIGHT OR REAR LIGHT FUSE

CHECK FUSE.IF GOOD YOU HAVE A BAD GROUND OR FAULTY TURN SIGNAL FLASHER.FLASHERS LOCATED ON THE INTERIOR FUSE RELAY BOX.

chevy uses a link from the key lock in column the the switch under dash, 1 or two possibilities providing you have not had the key lock out, 1 is the switch under dash has loosened and moved
2 switch under dash has failed

If its white Check your water is keeping its level Could be head gasket bown.If its blue then its burning oil witch could be valve stem seals or piston ring wear,

As far as fitting in the truck, no problem. Yes you will need a new computer. Your best bet would be to find a salvage truck with a 350, get the engine & the computer from the same vehicle. Most of the sensors are the same although, best case scenario is to get a complete assembly out of a salvage vehicle, including all the sensors. Motor mounts are slightly different, but you can pick those up at a parts store.

If you use a motor with a carb, you won't be able to hook up all the necessary sensors and this will cause your Check Engine light to come on at the very least, and possibly interfere with some or all of your gauges. (Remember, everything is tied together...including the gauges)

Hope this helps.