Here are a couple of areas to think about, Hopefully others will comment also.
1. Valve springs. FMS springs are good up to about 6200RPMS it seams to me. Given a larger buget I would do some study on valve spring makers, comp cams, crain are two, and replace them.
2. This also might be the time to change over to a stud type rocker and install rollers. I really like the looks of Comp cams magnums, They are made of steel and seam to be of very high quality.
3. Head port work, These heads look like they could use a little pocket porting around the valve bore and valve guide boss. No big port shape change just a nice clean up in the valve pocket.
4. I do not know which cam u have. Mine has a B303 and I think a little more lift might really work well. The heads I have, GT40X type, flow much better than stock iron heads but many other heads, AFR, eldebrock, victor junior, and others have higher flow numbers. I think that a about .5 total lift might make these heads work better. They are about .45 now. You will have to check for clearance to the pistons but you will have the motor apart anyway.
This is a good time to think about replacing the 1.6 rockers with 1.7 ratio rocker arms as these would put you right in the .5 lift ballpart with a B cam.
I am not much of a engine guy but this is what I would change first with a SVO 302 with X heads and a B303 cam. I really think you can expect about 370Hp with my ideas. I would still limmit engine speed to 6500-6700. The FMS lifters will not like more than that.
Lastly if you are using GTD headers you MUST check exaust port match. These heads have a much larger exaust port than the iron heads that were used to mock up the orginal GTD exaust headers. I'm talking about the twin 4 into 1 type not any crossover,Crossflow type.
Depending on your buget.....well I am sure you can spend as much as you like building 302 fords. For a nice street motor at about 370hp or so the SVO lower end will be fine along with the alum X heads. The GT40X alum head motor just needs a few hundred more RPMS as it seams to run out of steam at about 6000RPMS. This can be done with a little port work and quality valve gear.
Oh I am using a RPM preformer and a 750 holley and I like this setup for a induction system. And make sure you are getting to full advance,34-36 degrees, at about 2500 RPMS.