[quote="Alaskan Tin Can"]For your stated mission it sounds like a 180hp 170B will work really well for you.
Here's a biased opinion but with real world numbers to consider
I've got a decent amount of stock 170B hours and have put some 180hp 170B hours in. I fly with and to the same places as many friends that have 180s and 180hp 170s. The 180hp 170 will equal the 180 in landing and takeoff every time with equal weight and fuel per hour* being carried.
I've flown cross country trips at 135mph side by side with my buddy in his 180 burning 13gph and I'm burning 9gph in the 170. And we both are carrying roughly the same load.
Some numbers:
180B - 13gph w/55gal usable = 4.23hrs
170B - 9gph w/37gal usable = 4.11hrs
Most early 180s weigh around 1650 lbs w/2650 gross = 1000 useful - full fuel 330lbs = 670 payload
170B w/180hp weighs about 1350 lbs w/2200 gross = 850 useful - full fuel 222lbs = 628 payload
42lb difference in real payload if you factor in the extra fuel weight
But you won't be using all that payload with your stated light loads. With you and fuel, you'll almost be at the empty weight of a 180.
Pricewise I agree with Hammer. I've got a buddy that bought a freshly rebuilt/restored 170B w/180hp 5 years ago for $75k with a 0 time engine and all the mods you have listed as wanting except for the avionics. STOL kit, float kit, LR fuel, 80" CS Hartzell.
Another buddy I was helping shop got a 170B w/180hp last year for $40k with the 76" CS Hartzell and fairly stock. It cruises fast with the stock wing. He looked at two other 180hp 170s for $37.5k and $50k. The one he picked was the cleanest of them.
I've always heard from 180 owners who were previous 170 owners that the pleasure of flying was much greater with the 170.
Better forward visibility
Lighter on the controls
Easier ground handling
Better ski plane
Lower cost of ownership
Lower fuel burn
Buy one that's converted and then upgrade from there.
Not like I'm biased towards 170s or anything

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A 180 should go a lot faster than 135 on 13gph.