help with mods for my t-bird

I have a 1995 with a 4.6 in it. I want to get some gears in it........I do a lot of highway driving..... should i go with 3.55 or 3.73? Can I pull a rear differential out of another car? Is that easier to change than the gears inside? I am getting an aluminum driveshaft from a mark VIII. Maybe the differential is usable also? Do I want posi?
I'm also thinking of a shift kit, but I heard you need a tranny cooler with one. Is this true?
And finally I was wondering about chips. How do they work? Do I need to program them myself? Do I need to do all my mods before I get a chip or can I add them after? For example.....If I put a chip in what happens if I decide to upgrade my MAF?
Sorry for all the questions, I just wanna make sure I do things right before I get too involved in something.

If you do allot of highway driving 3.55 would be better but there won't be an incredible difference between them and the 3.73's I would go with the 3.73's personally... I know allot of peopel with them and they all like them. As far as changing out the diff, might be easier, to just do a set of gears you need a dial indicator so you know the gears are set in perspective to each other correctly, if you don't you'll break the gears. As far as the chips go they all usually come tuned, but if thats all your doing you may not see that much of a gain from it, after gears the next upgrades to invest in at intake and exaust, a full header back exaust is worth allot on these cars, plus if you good a good CAI with the gears and the exaust it will feel like a completely new car. Then start to look into the chip after that to maximize your newly improved flow. With all of that done your car will defineatly be allot faster. You should including the new diff you probabaly won't have to spend too much more than 1000, 1500 tops.

I have a 1995 with a 4.6 in it. I want to get some gears in it........I do a lot of highway driving..... should i go with 3.55 or 3.73? Can I pull a rear differential out of another car? Is that easier to change than the gears inside? I am getting an aluminum driveshaft from a mark VIII. Maybe the differential is usable also? Do I want posi?
I'm also thinking of a shift kit, but I heard you need a tranny cooler with one. Is this true?
And finally I was wondering about chips. How do they work? Do I need to program them myself? Do I need to do all my mods before I get a chip or can I add them after? For example.....If I put a chip in what happens if I decide to upgrade my MAF?
Sorry for all the questions, I just wanna make sure I do things right before I get too involved in something.

I'd go with the 3:73's. You wont lose much MPG compared to the 3:55's. Yes, its possible to pull the differential out of another car. The 99+ Mustangs would work. Actually, I think any pumpkin from a 8.8 equipped car would work. Dont quote me on that though. Is it easier to change then the gears itself? No, The gears itself would be easier, because you wouldnt have to undo the drive shaft. But, in your case it wouldnt matter, and it might actually be easier to get a new diff/pumpkin, because on some cars, they come with a posi/Trac-Loc built in. Check your RPO codes, your car might alread come with Trac-Loc. As for the drive shaft, I've heard that you have to take out the transmission itself to slide the sahft out. Again, dont quote me on this either. As for a shift kit, I'd reccomend the J-Mod. Its the best there is, and cheap. It modifies stock parts, mainly the 1-2 (and 3-4 optional) accumulators and springs, and re-drills the valve body, allowing for more fluid to flow, giving short, hard shifts. And yes, I highly reccomend a tranny cooler (24,000 GVW). Stock, the temps are catostrophic, add in a shift kit, and you're just beggin to blow. I'd get the chip last, so you can fine tune everything together. If you put in a larger MAF after the chip tune, expect computer problems. Do a MAF upgrade first, then have a chip dyno-tuned by SCT.

The easiest way to take the driveshaft out is to drop the gas tank down about 3-4 inches. Not having much gas in the tank is a wise choice! If you are putting the same driveshaft back in remember to mark it and the flange on the differential before removal.

Here's your Huckleberry for a chip.

http://img.photobucket.com/albums/v502/Tigerstar/BlueOvalChips.gif (http://www.blueovalchips.com/)