If you want to ditch the electronic stuff, just change anything that is electronic. The carb that was on it was a E4ME rochester Qjet. The computer used feedback from sensors to adjust idle and cruise fuel ratios. The distributor
should be a plain old vacuum advance HEI.
Swapping to a non-computer setup should be as simple as swapping the carb and using a sledge hammer on the computer, but its hard to tell what all has been done.
Here are some things to consider: EGR has absolutely no effect on HP or TQ. It is only active during part-throttle where it introduces exhaust gasses into the intake to reduce NOx and help MPG. The previous owner probably disabled it thinking that it would add HP, but it didn't. The only problem is that the distributor is curved (and the carb's cruise mixture) based on the fact that EGR is present. If you remove the EGR, you'd have to richen the cruise mixture and/or retard cruise ignition advance.
At this point, you'll have to make a decision; determine first what you have in place, then determine whether re-adding EGR or retuning the distributor and carb is the easiest route.
The other school of thought is: if it runs, who cares?
The 305 (no offense) was a low compression, tiny-cammed, wheezer-headed engine. Seriously. Some of them were as low as 7.5:1 compression and had cams in the 170-degree duration range. There are ways to perk it up, but before you spend money on this 305, strongly consider the fact that you can swap in a 275 hp junkyard 350 for $300 and no one would know the difference.