replacing 3L

By 3L I am assuming that you mean 3.0 Liter. If you want do swap in that rig, there are a few choices. The first choice is the best one, and is the Toyota 5vzfe (3.4L) from the 4th gen toyota trucks (1st gen tacomas). This is a bolt in swap, you may use the motor mounts and tranny from the existing 3.slow, however you will have to get the wiring harness and ecu that came with the 3.4 also. This is an awesome swap and the most reliable. If you don't mind looking into other venues, then another option is the Chevy 4.3L (vortec/non vortec...doesn't matter) This is a very powerful swap (for anything short of a GM small block) and the tranny bolts right up to the engine, you will of course need the wiring harness from the engine, motor mounts will need to be either fabbed or you can search the internet for a kit, although I don't think there is one available. Hope this helps, if you have any questions feel free to ask.