If I may add my two cents here. Toyota 5L engines are pretty hard to come by these days, at least in decent shape, and even the ones that you do find are the EFI versions (5L-E). Like all EFI engines they have their share of drawbacks for offroading, specially when you factor in the that your swap will be done by a desi mistri. Morever they are quite expensive. Here in a Karachi, a Kabuli 5L-E costs around 175k-250k depending on the condition, and brand new one (dabba packed, supposedy auctioned by Indus Motors Ltd), will cost at least 350k.
Having said that there is a much cheaper and in my view, a better alternative than buying a 5L-E.
If you have access to a competent machinist and mechanic, get your 3L block over bored beyond the 5L piston size and then have it sleeved, using salvaged cylinder liners from a Volvo or some other diesel engine. The outside diameter of the liners should be more than the inner dia of your overbored block and the inner dia of the liners should be less than the dia of your 5L pistons. Gte your machinist to turn these liners of his lathe to reduce their outside dia and expnad their inner dia and then press them inot the 3L block and hone them.
I recommend this to you because the 3l and the 5L share the same block and the same stroke and same crankshaft, whereas the 2L has a slightly different block and cranshaft because of its shorter stroke.
Another upgrade I wiuld advise is swapping in a 10mm rotorhead on your injection pump instead of the stock 9mm one. While the increased displacement and the bigger rotor will cause a slight increase in fuel consupmtion, they will also result in a more powerful enine.
(I suggest you do these upgrades one by one so that you can personally notice the increased power and possibly increased fuel consumption).
Finally, if you have access to a pyrometer and a donor 2L turbo engine, you might want to even turbo charge your upgraded 5L engine. Dont try to turbocharge it if you dont have pyrometer to measure the EGTs at varying RPMs, lest your exhaust temperatures get so high that they cause serious damage to your engine.