So what are the options to consider for mounting the battery tray and support (in the stock location) besides welding both pieces in place?

Magnets.

























Or bolt it in using inserts like Rivnuts.

I welded the support in place but bolted the tray to the support. Put a 90 bend in a length of steel and tig'd that to the side panel. Drilled holes and welded two nuts to the bottom of that piece... which the tray bolts to. Then the typical one big bolt on the left side in the usual place to hold it all in place.

Take it out, fix the metal, paint it well.
Weld in the battery tray.
Buy a gell filled battery.

It will outlast the rest of the car

I did 5 sheet metal screws into the side panel thru part of the origianl tray that was still welded on. So double thick metal. The bottom was rusted out and cut off. With the bolt thru the mount, it's very sturdy.

Basically I postponed the part where I do lots of welding on the car right before paint...

Better to do the welding right before paint then right after paint!

Zach

The main issue with things like Riv-nuts and/or screws, bolts, etc., is that things that pierce the sheetmetal are a rust magnet. That raw edge of the hole will tend to wick in moisture and then the rust gets started. Once started, it progresses to full blown corrostion and rust out in the vicinity of the hole over time.

My preferred solution is to reloate the battery to the center of the Frunk for the following reasons:

1) It puts 40lbs of mass down low in the vehicle lowering Cg.
2) It centralizes that 40lbs mass which helps reduce polar moment of interia. This benefits transient handling.
3) It puts a little bit more mass on the front axle which benefits initial turn in.
4) Opens up the hell hole to make future service easier.
5) It removes the possibility of future battery corrosion in the hell hole. This was more important in the pre AGM battery era of the 80's. Less relevant today.

I did it on my 1st 914 and intend to do so on this 2nd one when the rustoration work is done.

Downsides:

1) I ran 4GA welding cable though the same grommets under the drive side door sill as the evaporative emissions hoses ran. Back in that era I was running carbs and ditched the hoses so it wasn't much of a loss. Will have to be more creative if I run FI and full evap emissions loop on this 2nd car.
2) Expense of the welding cable and having a shop crimp on approprate copper lug terminals.


I never had any issues with slow cranking and/or high resistance due to the longer cables since they were upsized from stock battery cables.