1. How much does DMUK sell them for, and install them?An engine like this would be stripped and rebuilt. We would comission Darren Bowker for the work. With all the engine rebuild, pipework, tuning work, recommended gearbox work (lower final drive and LSD) you'd not get much change from £10k
Depends how you look at it! The brakes are good enough to lock all 4 wheels on a dry road, and the suspension is very close to an early Esprit. SMCH's shocks and springs would be a very good idea.
2. Apart from chassis welding, would the brakes or suspension need to be changed?
400+bhp, depends on the car it's in and the gearbox it's mounted to. sub 6 seconds easily though with the right gearbox. Off the line, it wouldn't be great due to beign a turbo engine (relatively), though a standing 1/4 mile would be pretty impressive. For anidea of spec, look up the stats on a Renault Alpine A610 V6 Turbo.
3. Could you give me some specs on the engine such as 0-60 times etc.