wanted:gt40pheads.Also do pistons have to be notched when using these
heads,and will yella terra stud mounted roller rockers suit.

Pistons don't generally need to be notched but it will depend on what cam you run. Also depending on what motor you are running the pistons may already be notched. The heads use pedastool rocker mounts not stud mounts.

using crow cams 621371rh with .5054 lift &1:72 roller rockers.95xr8auto
standard 5Lwindsor bottom end.
looking for 350-400hp,anyone who has specs on achieving this would be
great.

OK firstly with GT40P heads and that cam the most you will ever see is 300-330hp depending on what other mods you have. The only way to push 400hp is to stroke it to 347ci and get a bigger cam or go for some higher flowing alloy heads and a much larger cam on your 5L. You will also need a good intake, fuel system etc... The stock EF pistons do have small valve reliefs and PV clearance should be OK if the GT40P's have their stock valves, if you go larger valves then you will run into problems. You will still want to check everythign while assembling as there are variations. Might want to consider the crane 2031 cam if you dont already have the crow, IMO it offers a little better power potential, has been used by many people and is designed for the 1.7 rockers.

Waggin has some GT40P heads and a Cobra manifold.

Send him a PM.

I was going to buy them but I have to spend money on a gearbox first.

looked at 2031 cam & the crow cam has more lift & longer duration.will consider getting a larger cam if someone can recomend a good choice.
Car has:cold air intake,genie extractors,high flow cats,2 inch twin exhausts with cross over pipe & ciptorque chip.
Will do:upgraded injectors,fuel pump,larger throttle body & intake manifold-probally gt40

The 2031 is a more aggressive cam, look at the 50th figures. Has a good exhaust bias and quicker ramp speeds both of which are needed with GT40P's. Even with the 2031 you wont crack 350hp with the combo you are planning but you will come close if the tune is right. The 621371 is a tame cam, sounds almost stock but it does go alright, I used it in an engine with nearly identical specs that you are building and was fairly happy with it but I recomend something a bit more aggressive. If you want another step up, go for the Trickflow 51402000 (499/510th 221/225@50th), its a very nice cam IMO with a reasonable idle (wouldn't want anything worse on a daily driver though) and can produce some really good power.

also considering AFR 185 heads,much work needed in fitting these

The AFR heads are really nice items. If you get the pedastool mount heads you can just use your stock rockers ands pushrods, otherwise witht he stud heads you need stud mount rockers, hardened pushrods and guideplates. The AFR's seem to produce around 20-30hp more than the GT40P's on a 5L.