As Sean has said in above post, go out & buy the "Roadster" book, officially titled " Build your own sports car, on a budget"
As Sean says too, the Roadster is a fully independant suspension chassis design,
I believe the cvh & pinto engined sierra,s have the type 9 gearbox whereas the dohc tended to have the MT75 box, yes if using the MT75 box then the chassis build is slightly different in the transmission tunnel area, not a prob as quite a few builders are using that box so help is at hand.
On a personal note
i,m using the cvh engine then once been on the road for a summer after IVA test will install a 2ltr zetec with bike carbs etc, a brand new engine can be bought for approx £700 & makes the car very quick indeed.
If you put your location in your profile there might be someone local to you who can show you their build/car.
cheers
andy
ps... as for cost of build.... mine will be on the road within a £3k budget