Subframes - I've built 16v conversions before, been running for over 10 years, road and track.
If you have the skills to go EV then you can easily modify the standard subframe. Whatever you buy off the shelf thats aftermarket you are going to cut and weld anyway, so why not do it with the OEM mini one?
Before you do anything make a jig for the existing subframe out of decent steel - basically you build a square frame that locates just 8 points on the frame - at the back it picks up on the top of the towers and the rear head board mounts - these you can actually weld to your jig. Look on the 16v mini forum for examples of jigs, you can use scrap steel.
At the front you create a set of upward arms - to these to weld washers which locate with the front subframe mounts and the tie bar locations - they just identify where they are located and are not attached to the frame.
Then get your angle grinder out and cut the whole front section of the frame off, plus the sides, take it as close as you can to where it meets the towers.
Now lower you lump in, look through the driveshaft holes in the towers and try as basic alignment with your eye of approximately where the drive shafts should run and be in good alignment.
Thats your only critical measurement - once you have that you can start hacking off the back of the subframe for clearance - the good thing is you can add extra strength between the towers further up, this also might give you engine mounts.
Once you have your driveshafts right and a rear mount just build the sides and the front of the subby back up. The trend now is for bent round steel tubes, 10 years ago it was just box section.
Use rubber engine mounts, either utilise the existing Nissan ones or use early land-rover ones that look a bit like a rubber donuts with a screw each side - they will easily cope with you power and torque and allow easy mounts to be made.
Hope this helps - took me a year of looking at it to work it out, but once you start and build forward its easy.
Edited by DomCr250, 04 December 2019 - 12:10 PM.