First, the disclaimer.... This is just my opinion !!
I would encourage you to look very , very carefully at maintainence costs for any twin before you buy.... Maintainance and fuel can be impressive !!
Some of the older 310s' had a wing spar AD that could be quite expensive to perform.... I know of a couple of 310s' that were grounded by the owner because he couldn't afford to get them done..... Make sure that this AD either doesn't apply or has already been performed.
For the mission you describe.... I would be looking at some of the more high performance , retractable singles with turbo charged engines.
Examples : Cessna T206, Cessna T210, Piper Saratoga ( don't know if it's turbo) or the newer Beech Bonaza ( A 36 , I think it's called ?? ) . I would guess that the Bonanza ( with turbo) and T210 would cruise nearly as fast as a 310 ( within 50 knots ??) . They would make good IFR platforms and would carry your loads and still give you good performance !
With the price of Avgas and the projected difficulties with future supply , I would personally avoid the thirsty twins..... If you can accept the performance of the Cessna 182 ( maybe look at the retractable gear 182 ) , that is a fine airplane.
I wish you well, fly safe ! mike
PS: I fly a '63 Mooney M20C , ( 147 knots, 180 horsepower, 10 GPH, mostly a two seater for me) ....fwiw