If the UC was a 6cyl or Starfire 4cyl itll bolt straight in if its a HQ-WB or LH-LX 253. If its a Commodore one youll have to change the sump/pickup and engine mount adapters.

If the UC was a 6cyl auto the trimatic may shift on the wrong side, UCs have a LH shift like a T-bar WB or Commodore but the HQ-HZ and clumn shift WB have a RH shift. Best bet is to get a LH shift trimatic and use factory UC T-bar and console. If you are stuck with a RH shift box any HQ-HZ or LH-LX trimatic T-bar will do the job but youll need a console. If you have the tools you can sway to UC shifter to shift on the RH side and then use UC console.

Factory LH-UC 3spd, Aussie 4sp or trimatic gearbox crossmember will work, as will speedo cable off one of these. You can use the UC 6cyl tailshaft but 4cyl is too long.
Get a V8 LH-LX radiator, throttle cable and wiring harness and you should be OK.
Torana V8s use a different exhaust manifold on one side so you may be better off using extractors.

Lastly, pollution equipment. Hopelully the 253 you have is after 6/76 so itll all be there. Just hook up to the UC canister as per factory HX, HZ or late LX 253. If its an earlier 253 it wont pass rego without all that stuff and its a lot to change - heads, inlet, carb plus other stuff.

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