7 1/4 to 8 1/4..... easy?

Well i fryed my spider gears on the ol' swinger....

It is a 7 1/4 rear at the moment (turned by a stock 318/727)....

I found a 8 1/4 at a scrap yard in another swinger (same year) for $260 out the door.... But i dont know if it's gonna require modification in order for it to bolt up....

i did some measurements and they are both the same length backing plate to backing plate (50" give or take)but the 8 1/4 sit's back a little farther than my 7 1/4 (closer to the gas tank) and it's also 4" longer from the inspection plate to the u-joint yoke.... will i have to modify anything in order to squeeze this bad boy in there? do i need a u-joint conversion kit? I need to do this tomorrow so any help would be GREATLY appreciated, thanks!!

Alex.......