Lets first skip to your last sentence....."What's remarkably expensive" to you???
Probably something like what you're planning, given your other comments.
I don't have an open budget, but we are working with enough to build at the level we currently do.
Currently I am in talks with Art Morrison for one of their chassis. The Chassis with a IFS and IRS is around $25us A big cost of that is the IRS. So replacing that with the Tesla is possible.
Builds of '41 Willys pickup could be anything from making a beater street-worthy for a few thousand dollars, to building a completely custom vehicle - which happens to look a bit like a Willys pickup - for hundreds of thousands. Even before I saw the price, just the mention of a complete Art Morrison chassis made me suspect that you'll be well up the range, and Tesla suspension parts are likely to be a reasonable option.
I've looked at the Art Morrison IRS before, and it looks like a nice design (using GM hub carriers from the Zeta platform used by the Camaro and various Holdens); however, I think you would have trouble squeezing a Tesla drive unit between the mounting points of this suspension, especially with the wider (at the motor housing) rear units. There's a top view in the Hot Rod article
introducing this IRS; superimpose a Tesla drive unit and I don't think they'll fit, even with subframe modifications.
AWD?... it would add cost, but doesn't seem unreasonable.
I will get a true measurement of the front and rear axles when I'm back at the shop in the morning.
On a drawing from Art Morrison based on another Willy's they have done the front has a track with of 63.125" and 67.5rear"
So the Tesla could fit in the rear....
That sounds really wide for an old pickup... about four or five inches too wide at each end. I wondered if those dimensions might width across the outside sidewalls of the tires, rather than track width, but they're not wide enough for that. My guess is that the other Willy's was running much greater wheel front spacing than stock (so 2" less wheel offset, and so 4" greater track). If that's what fits, then I agree that the Tesla suspension would likely fit... in the rear.
The Willys pickup is significantly wider in the rear than the front. Apparently this was the result of basing the pickup on their sedan, and only using a wider axle at the rear (because the front body was the same as the sedan). Since that's not how cars are build now, width of Tesla bits would likely be an issue at the front.
285 days left to build this..... on top of the other 6 cars we are doing.
To me, a time crunch and hard deadline argue in favour of using a complete assembly of drive unit, suspension, and subframe, since you know they all work and all work together. The most straightforward might be all-Tesla at the rear, Art Morrison at the front, and rear-wheel-drive only.