Which rear shock

[Tractorman]

If a series 2 body has a series 3 engine in which rear shock should it have, please?

[gaz_powell]

I used a 305mm long adjustable (made by Hi Level) on my S2 with a S3 TS1 motor - no clearance issues

[solostax]

What dimensional differences are there with a series 2 and 3 engine?

[Warkton Tornado No.1]

What dimensional differences are there with a series 2 and 3 engine?

S2 is about up to an inch longer & that's what I would recommend for your set-up.

In fact, I personally use a S2 Shock on all my S3 road scooters & have done for decades!

The greater ground clearance is worth having & they work well, even by comparison to Gaz & BGM, both of which seem prone to eating their seals in very few miles.....