Question on SPF under #1000
 

I am considering a purchase of a SPF car in the 900’s number.

1. Were there any significant improvements made to later model numbers?

2. Are the dimensions and wheelbase of new models the same as the 900 number models?

Thanks

Try this link:
Superformance Mark-III Upgrades and Improvements

Terry

Here's a link to the features and improvements over time.

Superformance Mark-III Upgrades and Improvements

Get the latest number you can afford. - and keep in mind that although they are factory built , the installer and care taker of the car(s) has a great influence on how it works. --

Superformance chassis after #700 are all quite similar. Unless you are planning to install a newer modular engine and need more room under the hood you will have no real issues with an early chassis.
The important differences between newer & earlier chassis (in my opinion) are limited to:
A total windscreen replacement, but a "glass only" replacement can be done on the earlier cars.
A master fuse is not installed on pre 1040 chassis, but it's easy to add one.
A new design convertable top was introduced around chassis #1415.
A single fan relay was replaced with two individual fan relays, but once again, easily added.
The parking brakes are all marginal at best.
Nothing really wrong with pre #700 chassis either. The normal course of chassis development added to or modified things on these early chassis more frequently, like the braking or the wheels used, etc. But nothing that would keep me from purchasing a pre 700 chassis. I some ways, I actually like the earlier chassis cars better. But even these upgraded items can be retrofit to the older chassis. Check out the sales area here on CC. There is a beautiful early chassis for sale. Fully sorted too, which is a big advantage if all you want to do is drive the car... Contact me directly if you have specific chassis questions. My contact info is below.

Aren't the pre 700 chasis and interior of car smaller (less room) than ones after #700?

I believe the 300 series has most of the newer style interior improvements - consult the detailed list:
A link in an earlier post here leads to a great document the describes in detail the majority of the changes in the MKIII by chassis series. My intent was only to highlight what I consider to be the highlights of the factory related changes.
Seeing your prospective car close up, having the driver give you a ride, and then driving it yourself makes all the difference before a purchase. For instance; Dropped foot boxes may not make any difference to you if you are 5-'4" with size 8 shoes. I actually looked at 4 different cars before purchasing mine...
I think it's safe to say that car owners themselves develop a lot of great improvements to the standard chassis of any replicas out there, be they comfort or performance or safety related.
Enjoy the hunt.