Ron
Why stop at only one webber? Why not go nuts and have two 4 barrel jobs, or 4 2 barrel? The ultimate would be point fuel injection with a single ram tube per cylinder ( anyone else seen the Jag XK 13 lately!!!)
All silliness aside a 4 barrel Holley/Webber will give good top end but awful low end pull. Depending on model they do flow up to 850cfm, and the Rover V8 only needs 280cfm to run well. End result is that the engine gets over fueled and runs like a pig. Flow the heads, SD1 big valve heads are good, and free flow exhaust, along with a fast road cam will give the best increase in stomp.
Fuel injection is also very easy to do. I get my setups from a mob called Triumph Rover Spares in South Australia and for AUS$1650 you get the whole setup with the ECU already mapped with basic Rover program, yet with a laptop can be easily tuned up. Makes the car so easy to live with, just twist the key and go.
Electronic distributer also helps with reliability and tuning.
Cheers
GUY