9 inch rear end

i want to put a 9 inch rear end on my 65 stang. any suggestions from what car o truck am i better off with, without having to do alot of modifications  

57-59 ford , its the correct flange to flange width and will bolt right in, be sure to get the brakes , the u bolts and the , bottom spring plates.  

You can buy already made up 9 inch housings from after market vendors for your application but it won't be as cheap as finding an old 57-59 like shifthis suggests.
I found an old 9 inch axle housing off of a '67 'stang that I got at a swap meet and had a speed shop narrow it down about an inch at each end so it would bolt right into my '66 with no problems. I used the stock 29 spline axle shafts from my  original 8 inch rear end in the shortened 9 inch with no mods req'd. 31 spline axles are better but for 300 and under HP it won't matter. Its the stronger 9 inch differnetial pumpkin that matters most. You can buy the wider spring U-bolts for the larger diameter 9 inch axle housing at Mustangs Plus and other Mustang resto shops.  

Be careful if you go with shortening the housing.  It is not always less expensive then going to the after market unit.  The axles will also have to be shortened.  Not cheap and if they are tapered you will have to buy new any way.  Compare the cost of a used unit with ALL modifications required as apposed to a new unit cost.  I hate to spend more for an old unit then a new one!