The ute diff will handle it OK.
Dazzasute, if you have the 120Y borgwarner diff, you won't have any problems. If its the jap diff, it will probably get you out of the garage but not much further!

I use the Corolla BorgWarner diff, which is essentially the same as the 120Y's BW, but is 3" wider and matches the track of the front with Stanza struts fitted so you can use the same offset wheels front and rear without looking silly. And they come with either 3.9, 4.1, or 4.3 ratios whereas 120Y is only available with 3.9.

There are 2 different sump locations for 4cyl L series motors. The 180B's L18 & 1600's L16 have a mid/rear sump, and the Stanza L16 & 200B/Bluebird L20 have forward sumps - they are the ones you want. You can bolt the right sump and oil pickups onto the other blocks (L18 and early L16) but will need to either redrill the block or weld a tube into the sump for the dipstick.

I've heard of people having trouble getting the L20 under the bonnets, but I built mine for an L16 and the L20 fits in without problems - I've used some L20 engines over the years. I did pay extra attention to mounting the L16 as low and rearward as possible though.

The oil pump clearance to sway bar isn't much of a problem. The 120Y bar give you slightly more clearance there, and I have spaced the swaybar down from the chassis 8mm.

I use a Volvo 244DL radiator. it has the right height for the 1200 rad support panel, and right pipe locations for the L series. I use a slightly shortened Datsun 1600 bottom hose and a cut down VN (V6) Commodore top hose.