I am not a big fan of frame clips. Mustang II front ends are OK but I think the Dakota front crossmembers offered by http://industrialchassisinc.com/ are superior. Progressive Chassis in Ohio (I think) offers Corvette suspension kits for your truck. Progressive, Industrial Chassis, Art Morrison, and Fat Man Fabrication all offer complete frames for your truck. On the surface, the buy in looks high. But when you start factoring in time, particularly when you are paying by the hour, they start to look very affordable. I suspect the $1,500 quoted includes the labor and the cost of a fabricated crossmember but not the Mustng II components. If the quote is for a complete installation he will most certainly be using a cut out crossmember and components from an old Mustang II or Pinto. When he gets done you will have a scabby looking crossmember, small brakes, and components that are most likely used up.

Fat Man Fabrications is in your neck of the woods (Charlotte, NC). If you bring your frame to them they can install one of their crossmembers while you wait. You will pay more but you will get more. They can also help you with your rear end. I'd give them a call (704) 545-0369. Even if you don't use their stuff you will come away better informed.