If you are going to do an engine conversion on an RT, stick with a GT Turbo lump and make sure you upgrade the handling/suspension.
If you managed to put a 16v lump in there then youd have a car that had the straight-line pace of the 16v but without any of the other benefits of the 16v - at a price that you probably could have bought a half decent Valver for.
£1000 gets you a 16v lump fitted (rock-bottom minimum), plus brakes, suspension etc = at least £2000 in total. £2000 buys you a Valver; Ok, so it wont be the best, but it will handle and brake a LOT better and have all the uprated trim etc.
Go for the GT Turbo conversion mate. Lots of tuning potential. Or just buy a GT Turbo or a Valver!
My mate has just spent £10k sticking a Honda 2.2 VTEC lump in his car. It makes 220bhp with its race ECU (conservative estimate) and revs to 10,000rpm. But he stuck it in a Rover 216 Coupe!! The chassis wasnt even designed to handle Rovers own 200bhp turbo, let alone a Honda screamer!! It handles like poo, brakes like poo and to top it all off he could have bought three or four 220 turbo Coupes for the money!!!!!!!!
All due respect to engine conversions, but be sensible about it please!!