Morning All, Happy Easter,
I do believe you’re right nath, it does appear to be an 8. The lack of running boards is another indicator.
Blended, I did muck about briefly a long time ago trying to collate serial numbers - particularly for the HD series but soon realised there wasn’t the volume of machines and data needed to piece together any sort of system.
Your plans for Tractor are awesome! I can’t fully picture what you’re going to do but in my minds eye it looks positively ‘monster’ and goes like the wind!

Cheers,
P.S. the ztr is unfortunately on hold for the moment. My eldest has bought a property up the road and it’s taking up all my time. I’d got to the stage where driveability had been fully sorted and I’d fixed on a deck drive design and had started the lathe work for this. The deck drive design has been a challenge. I’ll get back to it soon hopefully.
It’s coming out for a play later today so the nephews can have a belt round on it.