Been buying and selling vintage garden tractors for 20 years. What I've learned over the years is a garden tractor you're selling is worth what someone is willing to hand over in cash that day

. To a guy just looking for a garden tractor to use around the property, a 73-78 Ariens doesn't mean anything, so I'm writing this from the perspective of a "Collector" and we're all
CHEAPSKATES when we are buying

.
Cosmetics, operating condition, and parts availability is generally what drives the price for a collector, in that order. Attachments really don't come into play because guys that collect/restore vintage machines don't generally operate them on a regular basis and the attachments just become a "show piece"
The S-14 is the older version of the Ariens GT series. The S-series machines were built from 73-78. The GT series started in 79.
https://www.tractordata.com/lawn-tractors/tractor-brands/ariens/ariens-lawn-tractors.html
The S-14's all came with the K321 engine, the variation was with the transmission and that is what primarily drives the price to a collector. Here are the transmission options in low to high desirability for a collector..... The S-14H is comparable to a Case 444 to a collector.
S-14G -- 4 speed gear driven (73-76)
S-14 -- Vickers Hydrostatic (77-78)
S-14H -- Sunstrand Hydrostatic (77-78)
With out seeing pictures, but knowing it does run, here's what I would expect to see as a reasonable price on a S-14 series, in average condition for it's age, with a mower deck and decent tires....
S-14G -- $300-$500
S-14 -- $500-$700
S-14H -- $700-$900
(Sunstrand parts are easier to find than the Vickers)
The snowblower is worth $200 +, depending on how bad a guy needs it.
Resorted to pristine condition a S-14H is worth $1,200 - $1,400 to an experienced collector.