davids2toys Dave,We all have different ways of installing and running our cars. I have been running in the rain. Water comes in under the front windshield gasket and soaks everything in the car. Both my ECU and MSD are getting wet. I have sealed both with RTV around the box seals and at the wires where they go into the modules. I use Packard connectors,(a GM thing, who I work for over the last 30+ years). To date, all connections have remained clean and good contact. Side note, if you get into a problem with checking out curcuits and they have packard connectors, GM recommends replacing them because of causing a weaking connection. We do a drag test to see if the connector is ok, No drag replace, Bending of terminals is a temp fix and doesn't last over the long term. Have to remember that the more amps that go through a connection the more heat is produces and we all know the heat causes metal to bend or weaken.
I wouldn't use a CB for this power curcuit. There shouldn't be a failure of the fusible link unless a major ground out. It will also be stronger on startup spikes on that curcuit. We have used them for 50+ years. I have 2 on my 79 TA that work just fine with 147,000 miles on them in all weather.
Reason for not using CB, Main one is a wire rub through, I have seen this, wire coating rubs through on metal part of car and arcs out to ground. CB blows and resets, wire still grounded. This can go on and on until the CB contact points inside for smoked or burnt off. Alot of wiring damage can be caused. I have seen it and been there once. I learned my lesson.
If you hook your power to the starter soleniod battery side and a ground wire to the heavy ground wire on the block, put wire protective plastic covers on them and ( VERY IMPORTANT ) may sure them are CLAMPED and wiretired to control movement, I see no problem.
Connections, as long and you use good ones, soldered and sealed or shrink tubed, you should never have a problem. Side note, some guys use KUNG FU grip to crush the connectors. You want them tight and soldered. Tightned to a stud or bolt holt but again not overtighten to crack the eyelet.
If you do good basic work, I see no problems.
Other notes Dave don't let the resistance thing run away with you. As long as you are in the .3 ohms and or less you have a good connection. .1 is idea. Doesn't always happen depending on type of wire, wrap of wire and gauge. Lower the better.
As far as MSD for the last 20 years they still gan't get the correct info on where and how to install a MSD box. I was told, no heat area and no vibration. Reason for mounting under glove box. Good freash air and out of harms way. They still have problems with caps and rotors.UGH!!!!.
YOu would have to check with Bob at ERA but I think the ground wire we use to the back of the head is for ground on all the dash lights and relays.
Bottom line, there is a little guy who sits on your shoulder and every once in a while he says, DON'T do that, or That's not RIGHT, you know kind, like the wife or girl friend and GOD is watching this also
. Listen and recheck or get a 2nd opinion.
I think I have tryed to cover it all for you. You are going in the right direction with the right ideas.
Rick L.