lets go simple, not rebuild the motor ok?
add an msd ignition coil and msd 6al box. use champion truck plug gold head (yes champs). gap .50mm. use a vacuum gauge and read from the vacuum advance, advance the timing until you have no vac increase, back the timing off to loose 2psi vac.
change the CAT!!!!
add a magnaflow muffler
25% increase, cheapest way to go! and future friendly!