If battery under hood is on a shelf bracket. I put my computer under the shelf. (put a cover plate between shelf and computer so any battery overflow did not touch computer or wires or connector. but its well hidden under there.
also I kept my original harness complete. I just rolled up extra tails of wire and connectors neatly and hid them under engine or or frame etc. two things by doing this. I was able to add stuff I later wanted like AC and some other electrical items. I provided extra wire. And I didn't have to worry about cutting a wire I should not have or messed up a connector taking it on and off. ok that is 3. plus GM spent a lot of money on engineers designing it lol
The way i have done all of mine is keep the stock little red positive battery connector box that bolted to drivers side head area but just cut the wire where it passes through the connector then just add a new ring terminal to 1 new battery cable and run the cable to the battery where ever you want which was stock under floor on my truck. I like it out of the way. As for the harness the ecu can easily mount on drivers side firewall like mine. Remember they are made to sit down behind and below drivers side headlight. I have done a lot of swaps and my first harness I modified in like 2012 is still in my car running today. I weeded out everything and carefully wrapped it all back up…..total waste of time and effort. Now i just leave everything and just de pin the connector at the ecu and leave all the wires taped up in the harness and never even mess with or disturb anything downstream. The only place i need to cut or splice is in the mini fuse/relay box to make my connections all from the oem “C2” connector.
Now you have me rethinking this situation have thought since my original battery box is bad to place on drivers side to have a shorter battery cable any pic of your under hood installation please.
Not a 49 but a 56 using this picture just to give you a engine bay concept. This was our super cheap budget build truck to get our feet wet. So we reused a lot of stuff including the fuse box from the LS donor. And I have used a lot of those already build setups for fuel pump relays, fan, radio, ac relays etc for all the other stuff we added. And it has lots of spares (built in ) And it matched visually with the big black battery on right.
Its sitting on the same battery tray as the passenger just added to driver side. The computer is under. this keeps the all stock harness drop outs LS side stuff on the same side stock. And like above, no reason to tear that harness down just pull the pins and wrap them up tucked away for later use. Not pictured is a plate that runs down from the bottom of the tray lip and covers the computer and wires under the fuse box. its held on by some wingnuts. We added it later so its not in this picture. But if you don't have the brake master on firewall and still on the frame you should have some room on the driver side of your 49. I also saw this on passenger side battery easy enough to extend. Or just leave it in stock location like a lot of guys suggested. Do a google search for LS trucks with AD or the years and change to images I scanned around and saw a few really cool ideas of where they put the computer. And even a few that put the battery in the bay.
My pics are in my “build” on here somewhere. Battery cable length shouldn’t be a issue. These new starters start up perfect and fast everytime. No problems like old hot big blocks or small blocks with voltage drop issues.
I kept my battery in the stock location. Mounted ecm to the firewall and I have A/C. I used the sanden mini compressor to keep it from hitting the inner fender on the passenger side.
