just wondering weather there are any andvatages in puting a j13 in a 1200 i have no idea on what the torque or power of the j13 is but its out of a '67 1300 ute

i would stick with the a12 the j serise are low on the revs they are also a bit hevyer dew to their cast iron head

Forget it as this would be a backwards step in my view.
If you want to replace the A12, then get an A14/15 engine & you will be streets ahead,.... really.

so puting it in would not make alot of difference because of its weight and its in abillity to rev as hard would a motor out of a 1600 be beter not sure what they are but i have one that came from a 1600 panel van

The J series engines were improved copies of a British engine that was designed in the late 40's or early 50's. The A series engines in our small Datsuns, & the larger L series of engines were new designs that were a substantial step foward in design & efficiency. If you want to upgrade the A12 in your Datsun 1200 ute [1970 & onward] then an A14 or A15 would be the most cost effective choice.
If you have some reasonable mechanical skills & a halfway decent workshop, then something larger & newer might be the go, but you will find that very few people, if anyone, has substituted a J series for their A series engines & with very good reason.

Have a read through the tech section to see what engines are regarded as good choices for your car, & why this is so, but don't go sticking something into a car just because you happen to have one laying around.

well the 1600 motor i have is been resently bored out and recondished and blue printed and is in a 1300 ute i have and the j13 is what was out of it and thought i would put that in the 1200 and i am now thinking of puting the 1600 in the 1200 ('73 sedan)