I’m not from Cali, but am very aware of what the laws regarding “legal” mod’s are in the area. Laws are close to the same in Mass...
You can go for a very strong build, if so desired. Supercharger, Twisted Wedge Heads, the best engine build for the buck, & legal, IMO, it the TrickFlow Top end kit. 360/350B. 2.02/1.60 170cc Intake port Assembled Heads, Track heat upper/Lower, Stage 1 Cam, Rockers, Pushrods, Locking Stud Nots.Studs/Guideplates, Gaskets, ARP Head Bolts. Gets you to about 315RWHP/330Ft/Lbs Tq. Accepts all your Smog, 50 State Legal. Strong, nice idle lope, Dynoed at 360HP.(Gross).
You need #24 Injectors, 70-75mm TB, CAI Intake, MAF Calibrated to 24lb Injectors. Headers/Exhaust.About 3,800$ for all. Too steep?.
As long as you’re not planning on removing your SMOG equipment, you’ll have no issues. The Explorer’s GT40/GT40P heads can absolutely be run, setup with new Springs, Retainers, keepers,Screw in Studs are much preferred, Viton Valve seals. More power with a Dual Pattern Cam from Comp Cams, 270HR or 274 from C.Cams, TrickFlow Stage 1 HE Cam, 2,000-5,500- pulls to 6,000, you could run a Supercharger if so desires. MFG advertises legality, you get a waiver Sticker,& they can’t bother you.
Gears are a great mod. 3.73’s, inexpensive. A cool air Intage, 70mm TB, Headers (Shorty’s are legal, LT’s are usually not). Buy parts slow you’ll need later, anyways. A 4 Bank Chip, you can switch back to stock, Car will run fine with a mild build, BAMA makes legal Tunes, too.
GT40P Heads accepts EGR, AIR injection from Smog pump, ported Lower, Cobra upper, Injectors, CAI, 24’s, Tune, exhaust, get you 260-275RWHP, What’s your Budget?