Oh let me take a shot at this!
1) I just got Toms HEI system and still need to install it. It looks almost original in terms if its overall size. About the same diameter but a tad bit taller. It does not have the coil located on the distributor head so you need to find a home to mount it. It also requires a bracket to mount the coil that YOU need to get. I think the only possible drawback to toms setup is the fact that it has a custom machined body to allow it to fit in the 235 block. So if for some reason you need to replace the body and or internal shaft you would need to do the machining again. However if you need to replace the coil,cap, wires, or other internal bit you can get them at any shop over the counter. Parts are from a mid 80's 2.8L system.
2) I currently have the Pertronix system. I had worn out points and wanted something simpler to maintain because I was in a lazy mood when reinstalling my old ignition system. I did not put the pertronix in looking for a performance gain. I have read posts about people saying that the pertronix system has fried on them and they have no choice to go back to the stock setup due to the fact you can't walk into any shop and get the pertronix parts. The pertronix system still needs a resistor. You still can do a external one but it has to be the correct vale, or you can buy the Pertronix coil that has one built in (the coil is yet another part that a general automotive shop will not carry in stock all the time) My current pertronix coil gets so hot you can't go near it and that scares me that one day it can go.
The actual performance gain if any between HEI and pertronix Ii can't comment on with proof in numbers and recorded data, but I have heard lots of good reviews from people going into a HEI system that the engine can start better, and run smoother due to the fact you can regap a bit larger and get a better burn (not sure if it's the placebo effect or the truth). Supposedly you are feeding more voltage with HEI then the pertronix. Most of the people who claim these gains are the ones who have done additional mods to the inline and not running stock. Im going to HEI so if something blows I can go get parts for it asap at any shop and any performance gains will be a bonus.
3) I have seen lots of distributors being sold on ebay that say drop in but like you I don't like the fact you can't get any real info on the units nor can you call someone to troubleshoot an issue. I have a feeling they are not made from scratch directly to fit but are just modified units to fit your application. You can find links just like the one posted on one of the other pages in this topic on how to mod a larger HEI unit to fit. You can buy a new unit from summit racing for a mid 80.s 2.8l and do the mods yourself. Or follow that tech tip link and buy the (new) same distributor from summit and mod that. I have dealt with tom now for a bit and overall he is a great guy. Granted I got frustrated with the carb issue I had with his units but that has been sorted out and is another story. He seems to know his [censored].
Last edited by wolffcub; 09/19/2014 4:22 PM.
