Thank you fellas. I really appreciate the advice and insights, very helpful. I'm making some (very slow) progress.
Quick update. I have my audi 016...new seals, diff bearings, etc...and updated with an 80% LSD from a 944 turbo. This is what I have been working on for the last couple of months....mostly because it's easy and familiar territory for me. I haven't yet found a strengthening plate kit for the backside of the gearset but one will pop up somewhere (or I'll make one). I have a lead on an kennedy adapter plate, along with some shift linkage that should work well.
I've been chewing over engine options. From a practical standpoint of just getting this project moving forward I think it may be best to just get a basic 302 SBF and bolt it up and get it installed and functioning. I would anticipate the engine coming out down the road for an upgrade to a stroker with all the nice go-fast bits, along with an induction upgrade (I'll start with a basic Holley then go to EFI).
I'll do some mock up with a foam/plastic 302 block to get the engine mounts properly engineered and placed - I can MIG and TIG weld pretty well. But overall, I think the basic dimensions are very good. The 016 is a bit more compact than the Citroen transaxle, with the output shafts closer to the bell housing face. The rear mounting points are in about the same spot. All good. My Esprit is an '88 with the inboard brakes so I'll have to get some later (89+) rear uprights with the ears for brake calipers. I should have started with an '89 but ah well, too late now. The existing 2.2L engine is a very good engine with no oil leaks and great oil pressure etc so somebody will want it for a Lotus project no doubt.
The SBF with accessories isn't any longer fore/aft than the Lotus 2.2 with accessories. As far as width, it should be fine as once the air box (on the starboard side of the engine bay) and the turbo piping (on the port side) is out of there it looks like there's lots of room. I'll have to relocate the coolant header tank, probably to the area where the turbo previously resided. I have no idea about exhaust system routing but I can start with mustang headers and custom build downstream from there. Clearance above will be tight, probably have to make some "adjustments" to the rear hinged deck ie. cutting to clear an air filter. I can make it look pretty and stock-ish. On the bottom side of things, the Lotus 2.2 has the bulk of the oil pan capacity located towards the back of the engine. Most SBF pans I've seen have the bulk of the capacity located towards the front of the engine. I might have to revise the pick up location, and perhaps swap a SBF pan fore/aft. Don't know.
There will be a bunch of detail work with regard to making all the gauges work, heating/AC system, shift linkage, etc. but I'll just take it one step at a time. My son is 8 so maybe we can work on it together and I'll have it done by the time he's getting his drivers license...
Now for removal of the 2.2L and Citroen transaxle....