I haven't worked much on small block chevys in the past 10 years, or so, but I got sucked in to swapping engines in my neighbor's truck. He has an 84 305 4bbl, that has well over 200K on the clock. It barely runs, and I suspect the cam is wiped out. He located a good used '88 305, that seemed to run good (he was able to drive it before it was pulled from the van it was in). Once I got it in the garage, I stripped it down, pulled the valve covers and pan to do a visual inspection- every thing looked better than I expected. We decided that since the engine was out, we may as well put rebuilt heads on it, and replace all the gaskets. Here's where the problems started: The first heads he got were 350 heads ( 1.94 intakes ). He took them back and, finally , got the right 305 heads. I pulled the old heads off, and lo and behold, they were 1.94 intakes! I measured the bore, and sure enough, it measured 4"- a 350. OK, I could live with that, but now he had to go back and get big valve heads. Since we didn't know for sure what engine we had, I told him to take the old heads, show them to the parts guy and say "I want these". After waiting 2 weeks for the second head ( I guess he wasn't specific enough ), I finally bolted them on tonite. As I was adjusting the valves, I noticed the valve cover bolt holes were missing- wrong freakin heads, again! Now, I know I can get an adapter to use the old valve covers ( or buy new ones ), and I know I can get an intake with the proper angle for the center holes, but I have3 questions:
1. Is there any mismatch between the earlier block and later heads ( such as water passages )?
2. Are the bolt holes on the front of the heads ( for accessories ) different from the earlier heads
3. Is there anything else I should be aware of before I continue with this little abortion?
Thanks for your input.

TG