Ok, I'll bite.
I have built a few of these, and have documented one build extensively, a RHD Westy with a 1380 and a CR 5 speed with a TranX LSD, 15" wheels and period correct Dunlop vintage race tires, right from the crate. This particular W11 was the 6th that I had experience with, and included everything that I had learned from my Westfield experiences, including the full reconstruction of my own 1380/LSD Westfield hot rod.
https://groups.yahoo.com/neo/groups/wes ... 1241634081
By way of comparison, my stable has included a Lotus 7 Series 1 (the car that was developed from the 11 "club"), Renault R5 Turbo 2 (I restore these for a living), Noble M400 (built the US press demo car), Morgan +8, and a bunch of other stuff, which includes everything from Alfa to Porsche, and a bunch of bikes (MV, Ducati, Laverda, Moto Guzzi, AJS/Matchless).
You want to install a Rover V8? In a Westfield chassis? Ok... Got it. I have a Rover V8 in my Morgan +8. Not unfamiliar. Mine's got a big dumb 4bbl and headers. Maybe 180 HP weighing about 1900 lbs. For comparison, my Westy has a 1380 spridget with 125 HP, weighing 1070 lbs. Guess which one is faster...
Stick a V8 into the Westfield, it gets a bunch heavier... This will underline several problems with the suspension as it is in the chassis present form. These problems are not so problematic with a light engine up front, and around 125 HP, but would be prominent problems with 180~300 HP. And, the chassis precise balance would be destroyed. As it stands, the Westfield W11 is properly balanced, and underpowered only by around 50 HP (unless you have a built 1380 or an X Flow, and even then, the X Flow is a bit heavy. Building cars is not like sorting an ill handling, front heavy contraption. Just my opinion. I could be wrong.
Why not start with a Westfield "Seight"? Then adapt the body to fit?
If you try to do the regular Westfield chassis, with a narrowed MG rear end, you will find that the suspension won't work (the rear arms are a bit short, the suspension travel a bit limited and, well, a balance problem. Then there is the room for the tires (vs. the frame and fully enclosed body work).
And... The lovely Costin designed body will be ruined by the modification to the front clam, and then... Cooling! My Morgan is challenged in this area, and if you try to put a larger radiator in the lithe Westfield/Lotus 11 front clam shell... I can already smell the coolant. Yes, I corrected both the Westy cooling problems that we have on the West Coast of California, and the Morgan's fear of high temps. I know what this is about.
I am not against doing engine swaps, but some cars are better served by a swap than others.
Lets take the Seight. Suppose you build a light weight S type Westy with, maybe a 230 HP Duratec? You save a lot of weight. Perhaps more than enough to offset the extra 50 HP you might get from a Seight (with an expensive engine build), and you would have a much better balanced car. One that would be easier to drive, just as fast, and one that you could drive faster, rather than having a car that might be "faster".
And if you put a V8 into a W11, what are you going to use for a tire? 5.00X15 rears? 4.50X15 fronts? Those are the ones that fit...
For the money you will spend to build this Rover V8 powered hot rod, you could build a Chevy LS6 V8 Miata (MX5, to you) that would be faster, better engineered, with better suspension, better weight distribution and have a proper kit to work with. Just talking here...
Or a Noble M400, a car that in my own experience, is perhaps the most capable sports car on earth, even considering the the newest is about 10 years old. Oh, and it only has a V6 Duratec with a couple of turbochargers. Faster than just about anything. Still...
I understand what you are trying to do, and appreciate the effort involved. It is just that this W11 chassis would need so much work, and none of it would fit beneath the lovely coachwork. What is the point? Nobody to fool with that, which is the best part of the engine swap strategy, right?
My little W11, lightened about as far as I can take it, will stick with a Subaru WRX past 100 mph in a drag race. That's surprising. And it still sounds like a Spridget.
I think that the idea of taking a Seight and perhaps putting a Westy 11 body on it sounds pretty cool. It would be the entry to building a Lotus 15 replica, which is something that we have wanted for years (as it has the IRS and a nice hood blister to hide many different types of DOHC 4s. But, if you stick to tires that fit beneath the bodywork, what are you going to do with all that power?
There are a lot of factors to consider here. For what you want to do, I am thinking that you really want a different kit to start with. If you are thinking of the W11 because it is beautiful, note that if you put a largish V8 up front, blister the hood, put larger front tires on it (eliminating the enclosed front wheels, an 11 visual treat) and cut up the rear to fit the larger tires that the extra power would require will leave you with a different car that you may have imagined.