ONETYPE CUSTOMS

When I find a 3.90 gear from a 620 that has the tag that says HF39. Will the 620 Diff bolt into the 521 housing or is there some thing that needs to be done first?

can I just change out the diff? or will I need a whole rear end?

THANKS KING!!!!

WOW angle down to the back that dude is twisted.. Angle on a lowering block soul purpose is to correct pinion angle . IT MUST ANGLE DOWN TO THE FRONT and anything over about a 3" block needs corrected pinion angle

stock with a 4.37 damn of course I want to change it.....My truck wont haul loads its getting a 6" drop...what year trucks have a 4.11? what years have a 3.90. thanks for the help

is there a tranny I can put in my 72 521 pickup to make it a 5 speed? or a rear gear I can get to change the ratio? sorry if it has been asked......