It sounds to me like he wants to get as much power as he can in the future and wants to develop a good plan to get there.
Stud mount rockers do not even require as much as a feeler gauge to install. They're much easier, not to mention stronger. If he doesn't want stud mount rockers, it pretty much eliminates TFS heads anyway since they only make heads for stud mount rockers. They used to support stock rockers and you may be able to find an old set, but then you might get a set with the bad valve guides.
TFS heads come with the guideplates, but not the push rods.
An E303 cam is just fine for street use and is emissions legal. To really benefit from heads or an intake, you really need a different cam. Whoever you choose as a manufacturer for your stuff, it's a good idea to tell them what you're after and get a recommendation from them as far as cams.
There is no reason to stick with the stock cam for driveability. There are a lot of performance cams that provide excellent power and excellent driveability attributes.
If the budget is
really tight, then I would suggest just getting the intake at this point. You won't get as much power, but you probably wouldn't get much power with just heads, either. You don't have to tear the engine down as much to install an intake, either.
Doing the heads, cam, and rockers all at the same time is easy since you have to disassemble a lot to just do the heads. It's just a lot you have to pay for at once. It will give you a good start, though, and will give you the most potential as far as performance.
The most important thing to do is to make a plan for where you want to go and the work involved to get there. It would help if you asked some more questions, though.
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351W 89 Mustang GT Convertible