With the H190, the tailshaft length would be the same as one fitted with a H165, so Andrew is right that a 1200 ute tailshaft will fit, but I think the problem will be finding one. Probably the easiest combination to get together would be an A10 (stanza,510,violet,etc) tailshaft, which is the same length as a ute one, with a 120Y (B210,etc) front yoke. Just make sure the universal joints are the same diameter, which is just under 1 inch.
You could also try using a 240SX rear yoke, which I think used a H165, & shorten the length of your existing tailshaft. I'd try for the first option, as you would still have the original tailshaft if things didn't work out.
Are you sure the H145 won't take the power?. I had a H145 open diff behind an A14 with 8 inch wide slicks & never even thought about the diff, though I did blow the A12 5 speed that I thought had a dicky throwout bearing, when it was the input shaft bearing. & I was doing 2nd gear burnouts on sticky rubber. The only reason I went up to a H165 was to get a choice of ratios that weren't there with the H145.