i've never heard of insurance bumping it for aftermarket modifications, unless you're talking about actually giving them receipts for aftermarket parts so if the car is stolen/totalled, you can get the correct value for it or whatever they call it (aka you dont get $5000 for a shell, and not a dime back for $8000 in parts you spent - they'll give you a percentage back based on the parts you have covered)...that WILL raise it some since theres more to insure.
i dont really need to see numbers. in fact i dont want to see..it will make me cry...
honestly do this:
-intake, header, exhaust,
-s13 cams...or dual 248* cams, or crower/PDM, etc.
-get a ROM tune. at this point you'll probably have the most power you can really get...
-then get an underdrive pulley, lightweight flywheel and a clutch, a 1 piece driveshaft and an LSD. this will free up rotating mass and you wont get "power" power out of it but it will put the power to the ground and you'll in essence feel faster, it works but im tired and not up for explaining it. get nismo mounts and a spl tranny mount, those help too.
-get a pair of electric fans when you do the pulley swap, and take the clutch fan off. hoenstly this doesnt free up much but it helps free up space and maybe the butt dyno will help you feel it a little bit.
after that, if you're truly into drag racing it, setup the suspension for it, remove some of the weight from inside if you can stand it being louder or ugly (aka seeing the inside of the panels and stuff --- i myself prefer full interior and it looking nice and classy)...get lightweight wheels and good tires for racing.
then if you want more power, jsut get SOHC pistons and put them in a DOHC block, pick up some 370 injectors and get the ROM tune retuned...that might net you some extra power and will be good for some okay times...no crazy 13's (maybe on slicks a 13.9 i dunno???) but it will be damn fun.
if you DO all that (or at least up to the piston swap part....i suggest going to an auto-cross or a road race session...you'll probably find that once you learn to drive it it will not only be even MORE fun...but you'll do surprisingly well....the 240 likes to turn and handle, even though going straight is fun in itself.