whats the correct resistance of a 1200 ute fuel tank at full and at empty?

Don't know what resistance the fuel tank has should be the same empty and full however if your talking about the sender unit resistance then as close to 0 ohms as possible at full and probably about 100 ohms empty.

im after exact measurements not guess's but thanks anyway, some senders can also start at 60 ohms and go well past 200 ohms.

Checked in my factory B120 workshop manual and doesn't list exact resistance, in fact doesn't even mension it at all, thats why i gave you my from memory guess.