1989 Blazer S10 engine switch

First and foremost, I am fairly ignorant of all automotive engineering beyond changing my own oil, so I came here to ask you experts. I have an 89 Blazer s10 with a 4.3L V6 with 250,000+ miles on it. Would it be worth a rebuild kit or should I just get a new engine? If I need to just go ahead and get a new engine, should I make it easy and look for a new 4.3 or should I beef up to a V8? Which V8 would be best-suited for my SUV? What transmission would I need to get for this new engine? I'd really appreciate some input on this one. Thanks a lot.

First off your 4.3l engine is not worth rebuilding to me they are only good for commuting around town. in my opinion you should just go to jegs.com and order a 350ci edelbrock engine part#350-45900. The best tranny would be a powerglide full length tranny part #890-73250436.