[xlr8or]

I would pull the coil wire and run a compression check on that side. I didn't see it above but the firing order is 18436572 for a small block chevy.
Sounds like a sticky valve to me or hydraulic lifter issue.
May want to pull the valve cover when doing the compression check and watch the valves on that #8 to see if the push rod is going slack.
And definitely check plug wires for correct order it's easy to forget the difference mentioned above about cylinder numbering if you work on both blue oval and bow tie. You may have two of them crossed and that one was just the most obnoxious.
also might want to verify that the #1 wire is on the correct post on the distributor. It is definitely possible to make the car run with them all 1 post over it just makes lots of exhaust pops and carb flashes..

PS: Have you checked the timing? if your way off it may indicate the plug wires are one post off.