The old style timing cover with the dipstick provision is available in reproduction form and is offered by many vendors. Unless you are going to use an electric fuel pump, you will need to use the old style cover. The newer covers don't have a provision for mounting a mechanical pump. You also need to use the original front sump oil pan or one like it. Most of the late model 5.0 HO engines used a pan with a kind of split sump. One sump a little larger than the other. This is not the pan that you will want to use. It is designed for the Newer Mustangs. Both the old and new style pans hold the same amount of oil. 4 US quarts plus 1 qt for the filter.
Canton Racing Products makes a deep front sump oil pan to fit your car that has a provision for its own dipstick. It holds 7 qts including the filter. This is the pan that I'm using, but I have the factory design dipstick in use. I believe that Milidon also makes a similar pan to the Canton. More oil capacity contributes to more effective engine cooling.
The side of the block dipstick hole can be plugged with a small sized plug that looks like a tiny freeze plug. It comes with the new old design timing covers, if you buy one. The block hole can also be threaded and plugged if you choose.
Hooker makes a good line of headers for the Mustang. There are several price ranges and the cheaper ones fit and work nicely. It is best to install a crossover between the two exhaust pipes. This helps to balance the exhaust pulses and aides in torque production. The sound of the exhaust will smoothen out, too. | 
