Ford 9” limited slip for challenge budget?

Open diffs suck. What is the best (cheapest) way to get limited slip for cheap? 
also I'd buy a lsd carrier if anyone has one for sale. Pretty sure this is a 28 spline but I'll check tomorrow. 

Weld it and don't tell anyone?

my challenge budget 9" consisted of a disgusting rusty $35 donor axle from a mark V, $105 clearance shafts, a free 3.25 open center, and trading the donor axle center section and 2.xx gears for a supposedly good 28 spline limited slip.  I'm not sure i could replicate that again if i tried for years though.  
 

craigslist seems to have used ones for $200 all the time?  

I bought an 8.8 rear end, complete with LSD for only $80. Would changing midstream cost less than finding a 9" LSD?

Manage to find a factory trac loc center section in a junkyard somewhere 

In reply to Patrick :

Dang. That is a good recipe. And one I doubt I could replicate. Welded diffs are allowed per current challenge rules, but street car and auto cross...

Deadskunk, the car is a factory 9" so swapping is less than ideal. Multi link too though I doubt the geometry is ideal for a racecar. Anyway, we got a donor axle for its gears but both are open. And the 9" has the benefit of us being able to drive 2200 miles on the cars 2.49 rear and switch in our spare 3.50 carrier with (hopefully) limited slip once we hit Gainesville. 
 

Summit has off brand lsd carriers for $339 which is expensive but not a total deal breaker if I can't find something else. Though maybe I get lucky and find someone with the correct spline carrier willing to flat-rate the thing to Utah. Still not sure this axle is 28 or 31. That's step one I think. 
 

I am always looking for 2.xx:1 9" gears.  Make sure you check the timing marks or leave it assembled.  2.50, 2.75, 3.00, 3.25 and 3.50 gears have timing marks.  MANY MANY times the marks are off by one tooth.

In reply to wheels777 :

Good to know.  I think the 2.lol gears I got from Pat are 2.75s.

I didn't realize anybody made nonhunting rearend gears!

Turns out it is 28 spline. Off to post a want ad...

barefootskater said:

Summit has off brand lsd carriers for $339 which is expensive but not a total deal breaker if I can't find something else. Though maybe I get lucky and find someone with the correct spline carrier willing to flat-rate the thing to Utah. Still not sure this axle is 28 or 31. That's step one I think. 
 

I was going to say for a challenge car, used TracLoc or Lincoln Locker is probably the answer.  That said, we've been pounding the hell out of the Speedmaster helical/worm gear LSDs that sell in the $350ish range on the road course (SCCA American Sedan, roughly 450hp+) and have had zero issues.  If you're buying new, that's probably the cheapest way out the door.

In reply to Rotaryracer :

Good to know on those. When I use the 2.lol gears, I will need to source another diff because they will be staying in the pumpkin they came in, and there is a bearing incompatibility with the carrier I have now.  I've been eyeing those but always felt a little leery.

The thing that sucks about 28 spline is all the cheap takeout diffs on eBay are 31 spline.