Ok, starting to feel a Mooney or a Deb might be a little overkill. What about a Cessna 177B or 177w with the 180hp conversion? I've flown an RG and liked it, but never went anywhere in it, just local.
350-400NM with 1-2 passengers as a typical flight? How often do you plan on doing this trip? I did a warrior II solo for 840NM round trips every other weekend and that was painful. Beat driving for sure, but boy that 110KTAS and that climb rate, oh the climb rate
. Meaning, it did it, but it wasn't pleasant. I'd overpurchase just a bit of capability and it should keep you happy for a long time. You can accomplish your mission profile with a warrior II, but it isn't pleasant.
As to Cardinals. Stay away from the 68' 180HP conversion 177s. They retain the original 2350# MGW even after the engine upgrade, so you're shooting yourself in the foot there. My warrior II had a higher useful load than that (2440# MGW) on 20 less HP. Science-wise 177s are structurally identical to the As and Bs (1969 177As are 177Bs with a fixed prop, though they retain the earlier sleek NACA wing airfoil common with the 68' 177 btw), but the STC holders never bothered with getting the increase in the MGW, so there it sat. The As and Bs are 2500# MGW airplanes. The 177Bs are overpriced for what they give you IMO, which is a slightly faster Piper Archer. They are great for the cabin comfort though. 48" cabins and a garage for a back seat. Doors are garage sized too. Just a dream for passengers.
Frankly if you're gonna go Cardinal, go RG. 135-140 KTAS on 9-10.5gph and enough useful load to do your 3 people mission comfortably and very attractive block times. Now, if you can find a significant discount on a 177B over the going rates for 177RGs, then sure go for it. I just don't see any niche on the 177B pricing. Lots of faster airplanes with more HP and higher useful loads in the same price range. Cardinal pricing is cult pricing.
Your mission is very similar to mine. From my experience you should calculate your yearly trip usage based on nautical miles, not hours. That really will dictate whether you realize the economy of gear costs versus big engines on fixed gear. A fixed gear 4-banger is a given on being the cheapest option, but you gotta ask yourself what premium are you willing to pay for comfort over 400NM. 100 mile burgers? Sure, stuff yourself in a stock 172, but over 350nm with the ladies, yeah you gotta up the ante a little bit. A Mooney F is not going to set you back any more than any other retract in it's class and will keep you happy, but the cabin comfort is something you have to determine for yourself and your passengers. I'm willing to go a little slower for better cabin comfort (cardinal RG, 182 or Arrow). Agreed, the six cylinder birds are overkill for your mission, but it might still prove economical DEPENDING on your yearly miles flown. If you intend on putting less than 10,000NM/yr, forego the gear costs and just go big bore fixed gear. But at the same time, are you positive you won't have years where you wish to up your mileage? That's where the retracts could shine, as these gas prices don't seem to ever go down.
I don't think a Mooney is overkill for your mission. A Debonair might be (six cylinders AND gear costs). If you're gonna go fixed gear go Pathfinder or 182. Otherwise go retract. Skip the fixed gear 4 bangers. Good luck!