The 4 litres are better, and more common, the MPEFI is the go, they are about 9:1 comp and in standard trim will go to redline of 5500 without any problem. The heads are very good and I wouldnt suggest any port work for street or lower level track perf, you could spoil the flow!
Cams are available from www.crowcams.com.au
and C.O.M.E. in Melbourne, the XR6 version has a bit more cam than stock and a bit more comp. The standard valves are 1.95/1.6 ports arent large but well shaped.
oil pumps are as for earlier engines, as KIWI said there are a couple of different ignition systems, best is TFI dizzy type thing with single coil.
The engines are no bigger than crossflow and earlier ones have pads so that earlier mounting will bolt up, starters are on intake side and are same as ALL Falcon sixes.
These are good engines and the XR6 version puishes a 1350kg falcon into 15sec, so in a light stang should be faster.
Dont start planning to ditch the stock stuff, the XR6 has the stock iron exhaust manifold and 2.5 inch header pipe just like the more cooking versions.