Rock on, guy! Long live the body-on-frame beasties!
If I were to use the stock block on my '90 Town Car and I had the funds (and spare time) to invest in it at will, I'd bolt up the following:
4.10 gears (4.30 might be a tad bit overkill, or maybe not) with LSD of choice
Medium-spicey shift kit of choice
CVPI (Crown Vic Police Interceptor) aluminum or metal matrix driveshaft
11.25" torque converter from 99+ CVPI or Mustang GT
Mustang tranny servo (to allow for higher shifts)
CVPI springs front/MOOG cargo springs rear
ADDCO sway bars front/rear
Gabriel Spring Assist cargo shocks front/rear or VST's (Bilstein HD's tighten the ride up a lot, but at the cost of riding stiffer than a stock Mustang GT)
225/60/R15's or 225/50/R16's - trust me, traction isn't THAT hard to come by on a Panther car
Stock E7 heads/HO intake/cam/ECM
65mm throttle body (
BBK, Edelbrock, FRPP, whatever)
1/2" phenolic spacer (actually sort of necessary when flipping the intake
Crane Cams 1.7 RR's
19# four-hole injectors sourced from late F-150 5.0/early 4.6L
Fresh timing chain/gear set (since you'll have that off for the cam, anyway)
Jeg's or Summit O/R H-pipe (most X-pipes probably wouldn't fit up right without modification)
Two 2.5" Mustang flow tubes (MAC has them around $40) leading to Dynomax Ultra-Flows and exiting through custom-bent rear-exit tailpipes (stock locations, nicely concealed)
MarkVIII radiator fan with DCC controller
Underdrive pullies of choice (March, FRPP, BBK, whatever)
3g alternator (to support luxury accessories, and especially for rad. fan and pullies)
...and if you really feel froggy, hook up a 100-hp shot of happy gas. Low 15's/high 14's on motor, 14's for sure on the bottle. All of this list could be applied directly to your car, just the same. Nothing outrageously fast, but a heckuva lotta fun for a full-size cruiser, and great for priceless stares of shock from cocky 16-second riceboys at the track that get stomped by a full-size "geezermobile."
Did I miss anything?