Rough running and lack of power can be attributed to coil malfunction - The bad running may well be ignition related - Is it possible the new ignition coil has been wired wrongly? The low tension + ve terminal goes to the ignition supply and the - ve goes to the distributor - assuming you have a - ve earth car, which is correct for all TR6 s. If your coil has sw and cb you would need to know whether it was made for - ve or + ve earth system cars.
Whatever happens recheck each part, plug leads connected, points adjusted,etc.
Lots of luck
Peter W