need a bit of help...

so i have a 1969 dart gt 273/904 that i want to beef up...

first- off how do i identify my rear end..i counted 10 bolts..ive been told its not a 8.75 which i beleive because it doesnt look very beefy....

If it has a rear cover and 10 bolts it's a 8-1/4" rearend..
second- i want to work with what i have,im on a budget...i want to remove and install 3.55 gears and make it posi is this even possible with what i have??

Yes but you need some special tools. An inch lb. torque wrench, Ft. lb. torque wrench, yoke holder tool, dial indicator with a magnetic base, pinion depth tool. If you don't have these plan on spending $250~300 on them. You can most likely find a 8-1/4 that already has 3.55 gears with a sure grip (posi is a Chevy term) for half the money than it'd cost you to do your rearend
third- i just picked up a bad *** set of wheel's (small bolt pattern 4'')if im forced to buy a 8.75 rear end can i put my axels on so i can use these wheels??

No.. You cannot interchange axles from a 8-1/4" to an 8-3/4 but all A-body 8-3/4's are small bolt pattern anyway so it wouldn't be a problem
thanks alot i want to make it a decent street machine but not sure what i can use:icon_smi:

The 8-1/4 rear is plenty stout to take anything most any 273 can throw at it. Some guys running 340's run them with success. I had a 93 Dakot with a 8-1/4 in it that I raced for several yrs. running mow 14's and the 8-1/4 lasted very well.