Hi i'm new to owning a escort cosworth and looking for some help. The cylinder head gasket needs replaced and since the heads off was advised to do the valve stem seals etc. Does anyone know what the valve clearances should be as i bought it with all the mods already on it and has different cams. Also what is the best gasket to be getting? The car was built by A1 rallysport and meat to be running 500bhp but have no figures to back that up. I have listed the spec below.

7.4 compression ratio
machined pistons with valve cap outs
arp big end bolts
6 long studded block
multi layer head gasket
26mm inlet ports
24mm exhaust
isky valve springs on inlet side
bd16 inlet
bd14 exhaust
rs500 t4 turbo
wrc injector inlet
p8 pectel 8 injector ecu

Cheers.