Sorry the waterpump was a PITA, and the original plastic screw in the rad gets very brittle after a million heat cycles. It broke on me and I didn't trust it to hold pressure - that's why there's a bolt in the hole - should out last the rad. M42's are a real pain to bleed the air out of the cooling system - as you've found out. R3V and M42club.com are great on line sources for help.
Good luck with the car ... I really enjoyed it the last 7 years. Hope you have just as much fun with it.