How about buying some threaded stock that will fit thru the axle slots (3/8" ?) along with 2 nuts and 2 washers. Place the thread stock thru the axle with the nuts and washers INSIDE of the frame and start screwing outward to spread. It's the cheapest and simplest way I can think of.
Update: perhaps I misunderstood, this would be only for spreading the rear axle area not a specific area of the frame.
Law of Logical Argument:
"Anything is possible if you don't know what your talking about".
Last edited by langolier; 07-23-2015 at 11:11 PM.