Dumper to become timber forwarder

[sion.dovey]

I have a project to build a small timber forwarder based around a small 4 x 4 dumper, i've chosen a 2 ton thwaites with a duff engine (petter ph2). Its quite an old machine currently fitted with the old 4 speed forward/reverse 2 lever shuttle gearbox that was famed for its weaknesses. I had one of the same model a few years ago that preferred not to stay in forward gear. None of that matters much as i will be looking to transplant some other engine with a little more schnell into the machine along with an alternative gearbox, and that is where my first unknown is. I like the idea of a Transit DI, fantasticly tough engine and easily available, and always will be. But i would like to stick with the principle of the shuttle gearbox, though definitly not using the existing one (that if its any good is destined to be fitted in a humper dumper project i have), so i'm wondering what gearboxes i could start to look for that might offer a shuttle capability and at least 3 or 4 gears? I think i would prefer to avoid a torque converter as whilst nice they are a fuel thirsty addition and not really necessary for my purpose; though i might be persuaded otherwise! I don't mind a bit of engineering and wont have a problem to make plates etc to adapt one thing to fit another.

There are a couple of constraints, firstly the whole unit cant be excessively long, i can extend the dumper chassis back a little but not too much ideally as i will alreay have to a little bit to accomodate a radiator and possibly hydraulic pump driven from the crank front end. And ideally i would like to avoid introducing any complex technology, mechanical is best in my eyes, so just a simple shuttle lever on the gearbox would be my ideal.

I have noticed the early JCB 3cx gearboxes, which accommodate a Borg Warner velvet drive marine gearbox in between a torque converter and a very neat 4 speed transmission, and one other idea might be to fit something like the borg warner or another marine gearbox with 1:1 ratio between the transit clutch and bellhousing and the transit gearbox, which is not too long a gearbox as it has no 'tail' like some rear wheel drive gearboxes do.

But maybe theres another ready to use unit that would be much simpler that i might find on ebay or something for not too many golden coins?