[Joe Pass]

A lot of car rearends are used in trucks, for example my 56 truck I run a 12 bolt Camaro rearend and a Mustang 2 front cross member with 11' rotors 4 3/4 wheel pattern. It depends on what you want for the truck, on my 62 I kept the 6 lug rear axles with a disc conversion (6 lug). The 12 bolt is stronger than a 10 bolt Camaro rearend just by physical size. It cost almost the same to buy car axles/bearings as it does truck ones and you still have to move the perches. I like 6 lug application for my truck, but if the wheels you want aren't in a 6 pattern then a 5 lug car may be more desirable. It boils down to cost and personal choice.
Don't let a 40 year old Posi in a 10 bolt sway you, you can always install one later when its more affordable and upgrade to a more modern version at the same time.
If it were me I would do truck for truck swap keeping things in perspective and drive the truck. Up grade things as it becomes affordable.
I have a history with GM rearends and the real reason people use Posi's is for off road/racing apllications, so unless you want to run your truck at the track, don't bother with it now... my 2 cents...Joe