Lars,
I know I sound like a broken record, but I've been brewing on this for a few days, so hear me out. The pan is the limiter here. A pan-based car can be made to be very, very nice-- but as soon as you make that choice, you become limited by the practical. That's not bad, it just means the slate is not completely clean.
Everybody looks at an IM as a bit of a curiosity because they cost so dog-gone much. But the platform itself is what makes an IM magic. It's not the rollup windows, the perfect paint, the great materials in every place, or the fit and finish-- it's the fact that an IM is a tube-framed car with multiple suspension/brake/transaxle options. The biggest mistake I made in specing mine was to not avail myself of some of the more exotic suspension choices.
Phil's car has a 914 suspension and brakes-- a full 914 set-up. Bob's and Marty's car have 911 suspension, brakes and running gear. The difference between these cars and a car with a front VW suspension beam cannot be overstated-- they are just an order of magnitude better. I did not have them money for such things when I put my car together, but in hindsight, I'd do whatever I ended to to get the 911 front suspension under the car.
In the absence of this as a possibility, this is why we were all pushing hard towards a Mendeola-suspended pan for the first 100 posts or so in the various conversations regarding your (yet-unbuilt) car. It's possible to eradicate the "old-car" (in the worse sense of what that means) out of the car, but it'll not be easy. There are cars with a VW beam that come close (I think my car, Joel Schlotz's car, and Terry Nuckel's car, and my car are all pretty nice) that do just fine-- they all have new beams, built with quality components, with all the tricks.
As Terry said, a ball-joint front end is the baseline (NO LINK-PIN). If it's a pan-based car, the EMPI stiffeners are worth every penny. You'll need at least a stock sway-bar-- I've got a thicker sway-away, but stock would've been fine. Good bearings (US, Scandinavian, or German-- not Asian or Latin) make stuff work. I've got a VW Golf rack and pinion adapted to my frame, I think it's worth it.
Out back, everybody keeps talking about IRS-- and that's great-- but greater still is being able to run 5.5" wheels and disc brakes.
With a pan-based, traditional-bodied speedster, using readily available wheels-- you can pick from one of these options:
1) IRS, 4-1/2" wheels, disc brakes
2) Swing-axle, 5-1/2" wheels, disc brakes
Everybody keeps advocating for a "Door Number 3" (IRS, 5-1/2" wheels, disc brakes), which doesn't really exist unless you are willing to spring for custom wheels that move the hub outboard (more back-spacing). You could get 5-1/2" steel wheels re-centered by Stockton Wheels or somebody similar (Danny Pip did his own, but he's a beast). But if you want ally wheels, get out your checkbook. Coddington or somebody similar could make a set for you, but they would have a price-tag approaching the cost of a 4x4 ft section of the ceiling of the Sistine Chapel, or a ride on the Mars Mission. At that point, get them in 16" if you want-- it's only money.
The problem with the custom wheel approach is-- what do you do if you bend one? I'm thinking if you buy four, you really ought to buy at least five. Now the cost exceeds the GDP of a banana republic.
Staying with rear drums helps a bit, but it's not a compromise I'd be willing to make (nor is it one that you'd like to make, either). Other options (custom control arms and shafts, etc.) are expensive. Unless your choo-choo is really headed around the bend (like *ahem* "some people"), choosing a pan-based car means choosing swing-axle, unless you want to run narrow rims and/or drum brakes.
... and you know what? That's OK.
I'd advocated for a "modified Jim Ignacio" hakuna matata plan. If you build a car with a nice, tight 2110-- you won't outrun the platform. Get a nicely built 5-speed swing-axle, and some killer AL wheels from Vintage Motorcars, and a good 4-wheel disc brakeset with Wilwood calipers (AirKewld or somebody similar). Get a truss bar, the EMPI front-end stiffeners, a CB camber-compensator, a front sway-bar, some good oil-filled shocks. Get rhino-mounts and a Vintage Speed shifter for the transaxle. Make sure everything has been re-bushed and has good bearings-- and be 100% content with what this is, rather than what it'll never be.
It's good advice that I wish had been offered to me, and which I wish I had heeded along the path. Stupid-cool stuff is mostly just stupid. To 99.99% of the world, what I'm advocating is the absolute most bang possible for the money spent, at least on these cars.
