I had to leave, so sorry I couldn't follow up. There is plenty of stuff to draw on, there has been more then one class for V8 powered formula cars. There was F5000 in the seventies, and there was a recent CART class for the entry level cars, I think. Plus there have been F1 and many Indy cars that had V8's. I will include a Lotus V8 formula car picture below. Building a tube frame for this type of thing is sensible. I am using suspension ideas from cars of that era for my own build and combining it with later tube frame stuff which takes the modern roll cage specs into account. That's a big difference between the 60's - 70's cars built with V8's / tube frames and modern stuff.
As an aside I will tell a very quick story. Hypothetically I might know someone who brought his wife to the track for a fun weekend. The car was parked and some checking over commenced. Someone with one of those entry level CART V8's showed up and took the adjacent garage stall. I am unsure of the the car's history but think that's what it was. Wife settles into a folding chair and start reading a book.... Time passes, as it does. Practice approaches and it's time to get ready....
"We're going to fire this thing up, perhaps you'd like to step back."
"No, i'm all set."
"Really maybe you want to move"
"No, I'm OK"
Pause... Grind, Grind "VROOM!"
One heartbeat later, wife gets huge nose bleed and falls off her chair. There is blood everywhere. Not a good day... So, just saying this is a whole nother level your getting into....
You could buy a car like that easy. Old race cars are cheap.
From your post above, you noticed your Ultima had custom fabricated uprights. That's a good place to start thinking about things. I think there is a lot to be said about just aspiring to designing and building a good upright.
I just made a simple model of a Miata upright and noticing right away it's much shorter in height then my Formula Ford upright is even though the FF uses 13" wheels. I think the bearings are much smaller too, but haven't measured those yet though. On the FF the bottom wishbones and transaxle mounting share bolts. That's not possible with the Miata units.
If you consider looking at fabricating your own uprights you can look into "micro stub axles" for sand buggy type units. That would let you use 930 driveshafts and CV joints and bearings for you car with your design.
Here is the Lotus V8 Formula car. Formula cars are about minimization to be successful. The rear suspension shows how to connect to the frame with minimal points. You just need to be able to put frame where those points are. Not hard after you read the specs for roll cages.