67JET I am guessing you have in board brakes on your jag rearend? You also have the standard outter hub bearing assemblies. You don't have any pictures of the rear of the car underside. Decooney would be the first place to start with. He helped ERA make a Watts linkage for the SC cars. Mounting plate that bolts to the stock hub housing. You will need a welder friend to weld a bracket to the frame. The other thing will be getting the right length radius bar to connect the two togeather. It's not a big thing. If you can't find Duanes info, go back about 1-2 years and try under ERA threads. There where pictures of the setup. Contempary also made a Watt's linkage. They made a special hub for there setup. I run theirs but had to modify the links to work. I am sure there is someone else on here that makes special hubs for Jag rearends. Try looking in the CWI catalog for parts. The special GT-40 hubs on some cars would also work with a little help.
3 Things for advice, A stock Jag rearend is good for about 450/450 HP and torque. You didn't say what tires you are running on the back end. Are the tire pressures the same? Has the car been corner weighted with your wieght in the drivers seat? You didn't say which springs and shocks you are running in the rearend. A video of the car launching would help with see what the suspension is doing. The alignment of the car,(thrust angle) rear camber and toe of both wheels all effect how the car launches.
Jag rearends, Get a Support cover for the rearend, if you are going to keep going burnouts. It's a cover that acts like a girdle to put pressure on the main caps in the center section and stops cap walk of the carrier. If you keep this abuse up, the stub shafts in the carrier will start to twist. You said money is an issue at this time, Get your self another carrier ( center section ) with the same gearing if possible and have a 30 spline setup installed in the housing. CWI sells a 30 spline setup with either your carrier and changing the guts to 30 spline spidlers or going to a 30 spline carrier straight. This will also come with chromemoly stub shafts that are now good for 600ft of torque and HP. This is what I run in my car. 10 years and no failures after a defective hub bearing was replaced. You will need to have a breather for the Jag rearend if you switch the rear cover. Alot of heat builds up when driving.
If you are looking for more info,private e-mail me. Rick L. Ps 1 some suggestion, this car was never designed to doing burn out, road racing autocross, cruising. The amount of damage the drive train takes when you hole shot the car is brutal. I race, only do a small burnout in water to heat and clean tires for 1/4 mile racing. I walk the car out of the starting line and roll on the throttle. If you are going to keep doing this, you may want to look at a 9" solid rearend for the car. It's stronger with 31 to 40 spline axles, will take a ton more abuse, the parts are easier and cheaper to get. Without seeing a video of the car launching, the suspension and possibly the pinion angles may need to be checked and changed to help off set the wheel hop.