Yep if the 1.3 is in decent condition, Ive had a 1.3 SPOA samurai with 31x10.5 pull 70-75 MPH no problems all stock motor. Now there are some cheap things u can do like KN airfilter, lighter underdrive pulley, all this does make a difference Ive done it on 2 sammys. But the best mods you can do for it is tracker/kick ring a pinion grears in the sammy diffs, and a weber.
I have done this on my most recent samurai and its nice to be holding 7-75 in 5th gear.