Timing on a DX in a campervan

Hello all you knowledgeable people. I hope it's OK to as about checking the timing on what has so far been a great engine in my T25 campervan.

It had this engine when I purchased the van 9 years ago and I think was transplanted back in the early 90's from a mk1 golf.

I will be changing the cam belt in the next few days and wanted to check the timing is all correct.

I just wanted to check the process as I have the strange situation where I don't think the flywheel marks are the same as a standard mk1, maybe due to the T25 gearbox it's fitted to?

I do have a timing light that I can set the advance on however with fuel costs and fact its in a van I will not be using super unleaded 97 octane.

Can anyone tell me if I can do this without having a TDC or 6degrees before TDC mark on my flywheel to go by? Should I aim for TDC given the fuel I will be using?

And if anyone has a rough guide that I could follow in my situation that would be amazing. I am basically unsure which markings to use the timing light on. Thanks

Personally I would set the timing at 6 degrees and use super unleaded, there should be a TDC mark and( I happen to have just looked this up) the 6 degree mark is 12.5mm from it.
You could always determine TDC the old way with a piece of dowel, let us know if you've not done it and I'll try to explain.
Cheers

Super unleaded would just make running the camper too costly so need normal really. I’ll have a mosey later

Is it possible to use timing light on any other marker than the flywheel?

If I lined everything up to TDC ( cam sprocket, crank sprocket, dizzy) could I tippex a mark to the flywheel and use that?

If you are worried about fuel costs a petrol brickie is prob not the best vehicle to run…..

However a GTI 1.8 is prob more fuel efficient than any of the standard T25 petrols.

Set up for and running 97/98 octane will give more power and mpg than when setup for 95 so cancelling out the few pence per litre savings of 95.

My 1.8 GTI has an arrow embossed in the cambelt plastic cover and a notch in the crank pulley, prob not as 100% accurate as the flywheel marking but a good starting point