I've done this on my 99 GU RD28Ti and it's a worthwhile swap. I had a local diesel shop do it and they did a great job. The only other thing they have to do after the pump swap is run a throttle cable from the injector pump to the accelerator since the factory accelerator is a fly-by-wire setup. It may not provide the precise tuning abilities that the electronic pump would provide, but it will be reliable and there are just 2 screws to easily adjust the fuel flow and idle. I've seen several RD28T's over here that have had the swap to mechanical pumps.