Teh junkyard turbo was brought up and promptly shot down (I've got a pair of FD3s turbos). Though getting one to "work" is doable for $200 and a bunch of labor, getting it to be reliable and not kill the engine would cost more, as it would involve things like BOVs and waste gates.
From what I've read about Propane, it will actualy bring EGTs down and, if you use the right amount, be better for your diesel then just diesel. It makes the engine run more efficiently, burning more fuel in the chamber, turning that heat energy into mechanical motion rather then burning it off on its way through the manifolds. Cooling the engine may be an issue.
A biodeisel conversion would definately break the budget, since there is gear required for processing the fuel. Plus we'd have to brew enough for the whole race. It's in California, so this simply isn't practical.
The FPR adjustment sounds doable. We'd either have to roll rune it or pay for dyno time. Installing an EGT sensor/gauge counts toward cost, not practical.
The nice thing about Diesels is, you dont have to dick around with the right intake or exhaust, because more is always better. No worries of backpreasure et all, just make it big.
We'll want to set the car up to run forever, making time on reliability rather then speed. In the history of this race, 7 of the top ten don't even finish. If the car lasts, we'll get a top-five. The propane would be a push-to-pass set up. I'm sure our pack will be agressive in braking and cornering, but you can't pass if the slow cars walk you on exit. This will be just to get by, 3-4 second bursts. A grill tank would be enough, we're allowed unlimited spares, so we could just change it out when it get's empty.