This doesn't matter. The firing order of the 5.0 HO motors are the exact same as a 351w order. That will not make a difference. You need to do a compression test with the rockers off. Don't worry, it will work. Air will get into the cylinders and it will give you compression numbers.fidstang said:
Your first order of business.
Take th eheads to a machine shop(or do it yourself if you have the meens-read straight edge and feeler gauge) and make sure the heads are flat, and not warped.
Get a set of ARP head bolts, or studs your preference.
Bolt the heads on with your standard autozone fel-pro head gaskets.
(Your TFS gaskets may be thinner than a factory gasket, thus holding the valves open)
Do a compressio ntest with no rockers, if all is good, bolt the rockers down and torque, then do another comression test.