You want a set of the good 68-70 B body BB HP exhaust manifolds. Streetmaster used to (maybe still do) offer swap mts for this. problem area is the trans tunnell. with the 727 you MAY get by with flattening or grinding down (which is better) the pinch weld in the slope of the trans tunnel & you might even have to cut & lower it for trans fitment. Best would be to cut down a 904 & use a JB ultrabell (my plan for my upcoming 63 valiant convert/451). Alum heads/intake/radiator to reduce the front end weight. cut the sheetmetal for more side radiator exposure along with a bigger (wider) radiator. use a 67 up gas pedal/throttle cable (drill 2 new holes for it in the firewall, piece of cake) & for sure subframe connectors