hey doug, never heard about that engine but you can always do the basics,better free flowing exhaust(either custom headers and big rear tubes and good mufflers) or do some basic porting on the stock manifolds and same a real free flowing exhaust.
if just points upgrade the ign to a newer durapsark if they will work on the unit
the compression is probably low on the industrial style engine so if in good shape one could do a basic valve job and take a good wack off the heads to get the comp up a bit and some mild porting.
do these even have a 4 bbl carb or were they run with a big 2 bbl.
one can do the same here if no good intake avaliable some port work can help there too.
from my experience which isnt much, minor things on a big cubic inch engine get good results just due to plain big size of them.
i agree with half tanked that a 7.3 may be the way to go but how big is this unit? manual or standard? cause a non tubo 7.3 is no powerpack