Fond memories:
I used to pull a 16' volvo/penta I/O 4 banger ski boat with a 74 145 (b20f). That little 4 banger would grunt from 200 rpm and drag the whole soaking wet beer stinking wetsuit strewn trash filled mess out of the water every time. glorified tractor motor is right. Guys with "gnarly" rigs would grin and give the thumbs up. And then we would tow the whole mess back to LA from Lake Mead with 4 people and all our crap. The big hill between baker and vegas was a lengthy 3 rd gear affair very much best tackled at night, and the cajon pass was pretty rough on the way out from L.A. It was a very well maintained car, and the 74 FI system is quite a bit less problematic than the 72-73 system IIRC. But it is the same glorified tractor motor. I would add that I would not have even considered any of what we did unless it was a manual tranny car. A light trailer with 2 dirt bikes on it is no problem. I would suggest IPD sways, rims from a 164 (way cheap) so you can get 205 sections on the car, and perhaps IPD heavy duty rear springs. My 145 was set-up with said. The 4 wheel disk brakes on 140's are pretty good still. I would do what you are talking about with one.
I skipped the 245 turbo era of volvos in terms of ownership, but you can get a 245 turbo that will be a much better all around car for probably about the same $$ as a nice 145. 245 turbos can be tweaked to 200 hp and 200 ftlbs pretty easily with some help from turbobricks.com folks and everything is better.