This may be a bit late in the day for the OP, but I have some ID data to add here, that may be useful to others.

The design features of the chassis and deck, lead me to believe that these were supplied to Honda MPE by SupaSwift, and are identical to their 'Big Bob' model.

The different peripheral items fitted to the Hondas were: wheels, upper handle loop and blade disc/blade assembly.
Honda wheels are different in appearance only; they are 200mm OD and 1/2" axle diameter, as are the SupaSwift BB wheels.

Some measurements to help with chassis/deck ID, related to the chassis rails; all measurements are centre-to-centre.
Chassis Rail spacing: 330mm
Front to middle deck bolt spacing: 170mm
Middle to rear ditto: 150mm

These are from a known original Big Bob, ca. 1985.

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."