Yep, good advice for sure.
Wish I had known that many moons ago when I started modeling the (very) first design, got it all done in wireframe, then tube, and then realized I could never fit wheels/suspension to it without it looking like a daddy long leg.
The frame render you see is from back before I committed to the 13B/MFA60 6 speed combo, and was going to use the drivetrain from my wrecked tiburon.
I did end up working back from track width/wheelbase/engine/trans dimensions when I made it, but there would be too much work involved to salvage the model and adapt it to the final engine/trans choice. I learned from it though, so there is that.
Now that I have the engine/trans that I will be using, it has became alarmingly clear that I can't do anything until I have the adapter plate made and can pull reliable points off the entire power plant assembly.
This is exasperated by my track width requirements (50 inches or under) for the rear, and the axle placement along the engine requiring a CV with a jackshaft (or an engine running on it's side). On the Hyundai setup, I could have got away with simple shortened axles and been peachy. Complexity, but worth it in the end for me.
Currently I have Miata spindles for up front and I'm debating if I go Nissan FWD spindles in back to match the trans, or Miata rear uprights, since I'm going to need custom axles anyways. I'm leaning Miata, because they look to be easier to work with, and I won't need to make strut adapters. I'm deciding that after the adapter plate is done though.
I've got an engine model off grabcad that I've been massaging with real world measurements, and I'm in the process of digitizing needed transmission features.
The bell housing patterns that make up the adapter plate were pulled using a Bridgeport mill with a DRO and an axial indicator, I just need to find time (and space again) to cut the MDF and do a proper test fit before the wallet comes out for aluminum. Then I need to find time to machine it...
The idea is to have the entire rear suspension and engine in as small and compact a subframe/subunit as possible, and then either bolt it in or build off of it for the rest of the car.
This is the state of the current model, from the rear. (click to link to larger image in the gallery)

The subframe tubes are just there to give a bit of a boundry box at this point, since the dry sump needs to be completed and the adapter plate needs to be finalized.
I also need to refine my transmission model, since it's a bit off, and account for the intake/exhaust at some point...
The rear suspension is probably going to have to be multi-link with bell cranks and inboard shocks due to the track width constraints.
Anyways, starting to ramble a bit too much.