I am thinking about swapping out a 7.3 diesel to a V8 gas in my 1991 ford F250 4X4 Extended Cab Pickup. Would it be cheaper to rebuild the diesel or to swap out for a V8 ? If I swap out the diesel what all do I have to do ?

I would definitely rebuild the diesel. To do otherwise, is more trouble and expense; plus, you end up with less torque, worse gas mileage, and poorer performance.

Some body should smack you " no offense". Why would you want to replace a powerful diesel with a wimpy gas engine? Especially if it's 4x4. Just rebuild the engine correctly or have someone do it for you. Switching to a gas engine will be too much of a pain in the if you do it the right way.