Since your not worrying about staying original, why not drop a 350 V8 in? They are dirt cheap at about $1600 new (Jegs, Summit, etc.) and can make 250 hp and 300 lb ft torque (the 261 has 150 hp & 230 lb ft torque for comparison). Couple the V8 to the SM-420 and go up the hill with the rear you have! Fitting exhaust manifolds might be the only real issue...
Just a thought...
Mike B
