Stage 1 V8

Hello iff I was to look for a second hand chassis to repair mine could I start with a standard 109 would it have to be station wagon chassis I know the front end is different but is the back end all the same cheers ,rae

Most of it is the same.
The key Station Wagon difference is no tailgate hinges. However you'd really want to get as late a chassis as possible so it shares all the minor points. Plus you'd be welding critical safety areas at the front.

I am not sure where the OP is located ... but there is a custom galvy coil spring rolling chassis for sale in Northern Virginia USA.

I bought a new galvy chassis from Richards in the UK and had it shipped to me in Virginia. It was a bit of a bother to get it imported. Several of the mounting brackets and holes were not as exact as I expected. It took modifying the frame and a few parts to get everything to fit back together.

But in the end - I have solid fresh galvy metal.

But back to the original question - difference between station wagon and other chassis... I do not know and I am no help.

Everything forward of the centre crossmember except the chassis rails is different, and even the chassis rails themselves are reinforced around the gearbox mounts.
Front crossmember is right at the front (S3 is set back), and the crossmember under the engine is removable on the Stage 1 chassis. The engine mountings are different and in a different place, chassis towards the gearbox area is deeper, and the gearbox has a different mounting to the chassis.

You could modify a S3 chassis to suit: swap engine mounts, cut open the chassis and fit crush tubes for the gearbox mounting, modify the RH dumb iron to take the Stage 1 steering relay. Other bits like brackets for fuel pump and filter you could improvise or swap.

Luckily the bulkhead is the same part number!