Hello Chips,
I have a suspicion that the 4.6 produces more torque than the LT77 is designed to handle. The 4.6 in my Rover was fitted in 2007, and since then has travelled over 200,000 miles (322,000km). To fit into the P6B, either a P6B or SD1 timing cover, you can use either a P6B or later oil pump front cover, Lucas 35D8 distributor regraphed as the 4.6 requires less overall advance compared to the 3.5, 28 degrees as opposed to 36 degrees. You can comfortably set the timing to 10 or 12 degrees at 600rpm. Is your engine low comp or high comp? Owing to the way the engines produce their torque, the low comps are preferrable with auto transmissions, the high comps with manual transmissions.
The P6B sump and oil pick up are required, a spacer for the crankshaft pulley as the 4.6 crank has a longer nose. A true roller double row timing chain is vastly superior to the Morse type, so do avoid the latter. SU HIF6 carburettors are perfectly fine for all types of driving, BBW needles and yellow grade springs. Be aware that these needles are still too lean at various points, so ideally they should be polished by someone that knows how to do it, whilst the car is running on a rolling road. If that is not feasible, just try the BBW and one or two richer needles and see how they go. It is trial and error as you're doing something that was not offered by the factory, a custom order in fact! Adjust the float depths to 60 thou and fit solid butterfly valves, don't use those with poppet valves. The original P6B air canister will need replacing as the 4.6 requires from memory 30% more airflow. The nose that allows air to pass through is much too small, so are the standard air filters. You will need significantly larger ones if your engine is to breathe as it should.
There is a dowel on the rear of the crankshaft that from memory requires removal so as to fit the P6B flex plate. P6B exhasut manifolds will bolt straight up to the 10 bolt heads which are to be used with composite gaskets. Use a tin inlet manifold gasket.
Ron.