How to install an old HEI on '72 GMC Pickup

[slowboy]

I've seen a lot of post on what it takes to replace points distributor with an HEI [non computer controlled]. Things like needing to be calibrated for advanced curve and other things. I know how important it is to know these things, but is there anyone that can tell me 'how' to do these things?
A friend of mine gave me an old HEI distributor several years ago. As mentioned in another post, I'm one of those that thought that I could just drop an HEI in and receive all the advantages and results from this swap.
Since putting HEI in, my old 350's performance and gas mileage has suffered tremendously. I put new weights and springs on HEI, but didn't seem to help much if any at all. I don't recall if I replaced coil or not. It seems that I would have though when I replaced weights and springs. I was told to change springs to lighter ones to allow better advance, so I did. I put the 2 lightest springs in kit. This did not help either.
I put E3 plugs in hoping for improvement, but did not help. After reading previous post, I saw where y'all were running a plug gap ranging anywhere from .035-.050...and the initial timing ranging anywhere from 8deg btdc-18deg btdc. I bought new set of plugs and gapped then at .045, and set initial timing [after trying 8-10-12-14-16 and 18 btdc] at 16deg btdc where it seemed to do the best.
I also would like to know how to set WOT advance. I've read where a 'dialback' timing light is used. Never heard of this before, but apparently necessary on getting best response from an HEI.
I know this is a lot of information requested, and all advice and explanations are appreciated.
Thanks ! !

'just wanting to learn since I can't afford shop prices'