Either the 261 or the 848 head can benefit from installing the early Powerglide 235 1.94" intake valves and the 1.6" small block V8 exhausts. Then do a little pocket porting to the bowl area under the valves. That won't fix all the 90 degree turns in the manifolds and heads, but it will improve the breathing a little. Inline sixes in general, and stovebolts in particular can benefit from modifications that increase torque, not necessarily RPM or horsepower, such as increasing stroke length and compression and reducing rotating friction with smaller diameter rod and main bearings and lightweight pistons.
Jerry
