Can you give a few more details - is it a LWB or SWB series? LWB can be shortened a bit to fit onto 100", SWB you're into chopping the chassis about (doable but puts you on slightly dodgy legal ground over here). Check Corrode Finger's build for some ideas, if not on what colour to paint it
Ignoring the more recent UK SVA issues, 88" coiler hybrids have been done a thousand times over here using RR/Disco chassis and Series bodywork, here's just one example.
As for engine - if your gearbox was from a V8 then no, if it was from a 200tdi or 300tdi then yes. Does beg the question, why not stick with whatever was in front of the gearbox originally - the V8 will be a hoot in a Series, a TDi will have a bit more power and economy, both will be more reliable.