Fred is right about 86 and up. You don't care about internal parts, you may care about external accessories. Don't get all confused.
The tranny will fit most any motor. The 700r4 has two input spline counts. The correct torque converter will solve any issues there. There is a change in crankshaft bolt pattern.
1. The bolt up should not big a big problem, just the correct flywheel/torque converter.
2. You have an 86 and up. If you buy another, it's not an issue. If you by 85 and down, small issue. BUT, investigate and know about splines and bolt patterns.
3. If you buy 85 and down motor and it includes all the accessories, you don't care if accessories are compatible.
4. You didn't say if the oil was OK.
5. Check the 85 and down for same motor mount pattern on block as the motor you have now.
Bogging down can be FUEL DELIVERY.
1. Fuel pump
2. Gas cap not venting. Leave it off on next drive.
3. Floating garbage in fuel tank, carb, lines...hills make it move around and block.
4. Carb float level and float drop.
5. Carb (needle valve and everything else)
6. Timing screwed up
7. The hint would be that it runs good and then not, that's 1 thru 6.
Bogging 2.0
8. Old gas with water in it
9. Vacuum leak
10. Timing chain
11. Bad dizzy, (vac advance, gear, mechanicals)
12. Keep collecting info here on Stovebolt and the net.
