Top 5 A-body mods...

First five steps,?...
Fresh chassis,OEM style..
Upgraded drive line...( transmission, clutch, rear end)
disc brake ,front brakes,OEM style....
Subframe connectors, welded in..
Patience,in building a strong base,to build on.. Horsepower means diddly squat(& you look like a buffoon..other wise),unless you have a plan...

Big bolt pattern 15" wheels with 4 wheel disc brakes
Chassis stiffening via complete US Cartool package
Suspension upgrades (bars, springs, anti-roll bars & Koni's)
EFI'd hydraulic rollered 408 stroker
200R4 4 speed automatic with 3000 stall lock-up converter.

Expensive, but over a ten year period, still cheaper than a new car.