I'm thinking about putting together a squad of converted Space Marine Bikes or a Land Speeder.

Fluff-wise its doable, Guard had a speeder that was identical to the SM version back in RT. Theres also quite a few forum posts etc around about similar builds.

Does anyone have any suggestions for ways of making these models look more low-tech, as only the Marines get the shiney ones?

Would there be any way of using Sentinal parts to make a roll cage type effect for the top of the speeder?

Those old IG speeders had front seats that were compeltely open, doubt that would look any good.

Cheers,

Pete

Ooh, rollcage.
Yeah you could probably fashion one. But making it out of wire might be easier.

What do you think about an ork bike/war trakk pre-looting?

Bikes should be OK. I can also see a beach buggy type vehicle, or even a hummer for the IG being fun.

Oooh, A hummer..

Nice idea.. now to find a base model for conversion..

Given that GW is 28mm, are there any companies that make kits in the same scale?

Ooooh... you can buy a Ferret in kit form.. Now that is Guard-like.

A roll cage would be much easier made out of plastic tubing. Trust me, I have just done that self same thing for my Orks.

You could try using the Ork Warbuggy as a basis, and plasticard your way up from there.