I've been having the same issue Gene
It seems all the suppliers now only carry cheap or "Speed" replacement parts for them.
I have had some success by going down and camping at the counter of the NAPA dealer and going through his books for Echlin stuff. I tend to buy just about anything I see that looks even close to OEM spec ...
I've also hit a local 'Old's-Cool
' type auto supply store in a nearby town - the counter guys know me and 'humor' me if I go during slow times in looking up and pulling 'Standard' (brand) parts so I can look at them.
The biggest problem is Weights and Springs - the GM weight profile is very technical and has a definite response during operation I've not found in most of the "Speed"
I try to use GM weights and select springs to allow the curve I need ...
The closest I've come to a decent 'kit'
is the ProForm #66945BKC.
At least it looks pretty stock once installed ...
Summit has them for under $100 - http://www.summitracing.com/parts/pro-66945bkc
I've install two of them so far and they have both worked fairly well. I'm still not sure the mech. advance stuff is the best ... but they seemed to respond well after tuning.
Here is a Parts Diagram of a common HEI
Here's a site with some good info and guidelines - http://rmcavoy.freeshell.org/HEI.html
Hope some of this helps