I have a 1998 cobra with a vortech super-charger, afm power pipe, sct tuner, and bbk headers, my question is reguarding top end. my car is fast off the line but when i reach higher gears i get smoked by imports and camaro's, i was wondering what i could do to get more top end out of my motor  

Give more info about how much boost you're running, the tune in the SCT tuner you have, and what rear gears you have.  You should be able to tune it for better top end through the tuner, and then compliment it with different gears.  A good balance of bottom and top end would be 3:55's.   

currently i am running 8lbs. of boost and 4:10 posi. in the rear  

Ok, what trim blower is that Vortech?  You could pulley it differently because even with 4:10's you shouldn't be topping out so early.  If you want, an easy way to change the effective gear ratio would be to get slightly taller tires like 28 inches tall.  You'd have more traction as well and you'd have to retune the engine and speedo calibration if you do this. 

it has an sc trim supercharger, i believe it was installed in 98' i was looking at a set of 18X10's in the rear and 18X0's in the front with nitto 555R drag radials and looking at how much it would be to replace my 4:10 gears with 3:55's  

Sorry about being slow, TGiving put me waaaay behind on things.  Those 3:55's would help, or you could get slightly taller tires around 28 inches tall.  That'd reduce the effective gear ratio and then you could avoid the install headaches.  The SC trim shouldn't run out of steam like that so maybe it's the gear ratios?   

i appreciate the help and i will look into the tire and gear ratio situation thanks  

i started looking into replacing the gears and stregnthening my rear end and i was wondering if i could swap out my 8.8" with a 9", i was wondering if anyone has done this and how much of a problem it would be to do so??  

You can get a 9 that's been modified to be a direct bolt in but it's expensive.  If you have one modded on your own, you need to change the control arm mounting points, both upper and lower.  You might need the axle tubes shortened slightly as well, which means the axles too.  Either way is worth the time and money to do.