'70 Dart Swinger rear end swap

I am brand new to this resto business and need a bit of advice. I've done a lot of work on vehicles over the years, but I'm painfully inept at anything related to rear end work.
I have a '70 Dart Swinger that's currently in a whole lotta pieces. Started as a quick flip, but you all know how that goes... In any case, after buying a car that sat outside for 16 years (but is unbelievably solid) I decided to pull the motor to re-gasket everything, and from there it's snowballed into a strip her down to the bare bones and completely restore everything. I have the car on the rotisserie and dropped the rear end and springs out this weekend. Even though I'm staying with the slant for now, the 7.25 has got to go. A neighbor has a '74 Dart Sport (318 auto - but he's keeping that bit) that he's offered up as a donor car, not sure what rear end is in it yet. Any ideas from the crowd? Any chance without seeing it that it might be an 8.25? He also has a complete rear that reportedly came out of an '81 or '82 LeBaron. Don't have any pics to post yet, and information online is confusing - the LeBaron rear housing has a 10-bolt cover, but the axle housings are tapered from 3" to 2 1/2" on either side of the pumpkin. Some sites say the 10 bolt cover is indicative of an 8.25, others say that the tapered housings indicate 7.25. On a side note, at some point the front was swapped for newer discs with the 5x4.5 pattern, so currently I have two different size lug patterns front vs. rear. If for no other reason than convenience I'd like to have the same front and back without adding spacers. Please let me know what additional info is needed and I'll try to post some pics if necessary. Help????