Biggest problem with forced-induction in a Pantera is very limited access to the front of the engine for drive belts. Turbos avoid this problem but have their own set of troubles with exhaust adaptions, carburetion etc. Smaller B & M roots-type blowers will fit but are really suited for drag racing, not general street use, and the blower housing & carburetion/air cleaners reach nearly to the roof . Finally, IMHO any blown engine delivering more power than a mildly modified 351-C will cost far more than $6K and probably not be wholly reliable. The old dual-Roots Magnechargers that Wilkinson used to install on Panteras cost around $20,000- in 1987, and delivered about 8psi boost or maybe 450 horses As an alternative, PreProformance in CA offers a 512-inch big-block Ford with alloy heads etc that is very near the wt of an iron 351C, fits in a Pantera and delivers over 540 horses with a mild cam & a 4bbl, for around twice your budget.