Those rules are very open but if your using a Mustang, 2000# is really light and depending on the rules might be hard to reach. We had full bodied cars with stock floor pan (fr to rr) and came in about 2400#, 2200# (depending on rule) can be done. Biggest thing to remember is ounces equal pounds.

> Must be located in same location as stock engine for model of car
Make/modify the engine/trans mounts to be solid.

> Any flat top pistons
Use good pistons, I like Wiesco. Race engineering has some extra light weight pistons. Also we had good luck with the Total Seal rings too, they seal just like the name says.

> Any steel rods
Run the longest aftermarket rod you can. 5.7 is standard but 6.0 are starting to show up more. The pistons on longer rods are lighter too. Rule of thumb is the shorter the track the shorter the rod, but my theory is if you can get more power from long rods run them, the cam will need to be a special grind.

> Crank must have stock stroke
Doesn't say you can't lighten it, a knife edge crank will get you off the corner very fast. Don't forget that an aluminum flywheel will get rid of more rotating mass. Rotating mass is the enemy and do what you can to get rid of it. Balance everything together too.

> Any non Aftermarket heads
Doesn't say anything about not porting it. A D-port is the best canidate with a esslinger port job.
Best to talk to Esslinger but the head can also be milled down about .150, this should give a little pop. I think our last engine had .010 off the block and .160 off the head.

> any steel valve of stock diameter
I've heard that 305 HO (Yes Chevy) valve will fit into the head, this would give you a BIG vavle head with stock valves. It does say ANY stock steel vavle. CHECK BEFORE DOING THIS.

> stock type intake manifolds
This is talking about a FI intake manifold and removing the center webbing. I've talked with people that say it WILL add HP but I've never run one. If you don't remove the webbing don't run it.

> .500 max lift cam measured with .025 lash at valve
This tells me that solid lifter or a roller cams are legal. A roller cam will give less resistance but not sure money to power is worth it at this lift.

Couple other things to remember:

1. get a racing timing belt tentioner, THIS IS A MUST.

2. underdrive pulley on the crank is a must to slow down the water pump.

3. an Honda alternator (very small) on the smog pump bracket (very low) will also keep the battery charged and life much easier. People will tell you is sucks power, but it also keeps a full charge on the battery, makes life much easier and actually might give you more power with a fully charged ignition system.

4. A SCATTER SHIELD IS A MUST TOO.

5. adjustable cam pulley