My guess is that you're on your own and will need to modify it quite a bit. I think the biggest obstacle will be because your Spyder frame is very different from a 356 plus the engine and trans are turned around. I can visualize the pull handle under the dash and it related parts probably working but after that, the down stream mechanism most likely will change. In my Spyder, I rather like the nifty little ratchet set up next to the shifter. I probably won't use it much but it's nice to have on occasion ...........Bruce
I'm trying to figure out what rear or mid-engine has to do with e-brake cables, other than maybe the length?
Do you have anything in your engine bay currently for ebrake cables?
We use about 3' of tubing that almost double 90s for the cables (More like 80 out of the tunnel and 70 back towards the caliper. Stock VW cable housings plug into it there and run to the caliper.
Pretty much the way Vintage does it. Through the firewall, about a 90 degree bend, then over to the trailing arm, another 90, and back a few inches. Cable housings from the tubing to either backing plate or caliper. I greased the cables in the tubing as well as the flexible housing.
I ran my cables forward between the seats to an aluminum bar with three holes in it. My cables weren't equipped with swaged ends(from Airkewld). I used VW throttle cable clamps to hold the cables. I used two nuts on the rear to lock in the adjustment, on 1/4-20 threaded rod. The threaded rod has a clevis at the e-brake handle end.
Since the calipers are self-adjusting, I haven't touched the cable length since the original install in 2017.