Some thoughts, Stiff.
(Actually, more like many, somewhat rambling thoughts. You might want to sit down with the beverage of your choice and have a read.)
I saw your other post which listed you as 6'2, 220 lbs, if I recall correctly.
I am 6'2", 240 lbs (34-in waist) and I can fit comfortably in most regular racing seats in terms of width which is approx 15'-16" wide.. Many race seat manufacturers also offer "wide" versions of their most popular seats
I have a secondhand Corbeau Forza seat which is not snug across but which fails to provide adequate lumbar support or thigh support. There are all kinds of lumbar solutions (pads from OMP, Sparco and other racing seat manufacturers) but the shallow front to rear seat cushion dimension is harder to address.
The most comfortable seats EVER for me were the Lear Siegler (sp?) extendable cushion seats in a friend's brand new 1985 Mustang GT. A quick manual adjustment provided perfect thigh support.
The seats were a common option in Fox body Mustang GTs and LX 5.0s (approx. 1982-1990/91, if my memory comes close) and on as a rare option on some 1985/86 Buick Regal T-Types and Grand Nationals.
The Fox Mustang extendable seats are pretty common, but even rough examples aren't as cheap as typical decent boneyard seats. The good news: reproduction Mustang seat covers are available in cloth and lesther, but these are often for both front seats and the rear bench. The bad news: the cover kits are pricey IMO.
Luxury marques like Audi, BMW Mercedes-Benz, and Volvo and some Japanese makes currently offer electrically-operated evtendable seat cushions as well.
BTW: Recaro still makes extendable cushion seats, but they are expectedly high dollar to go with the Recaro reputation. Recaros were also available on 1979-80/81 Mustangs.
In looking for a seat for youself, take the following items into consderation:
1) Do you need a reclining seat? How long of stints do you see yourself at the wheel?
PRO: more adjustability and comfort
CON: less rigidity can with high braking effort from serious loadcell pedals
2) Do you foresee yourself wanting more immersion which the addition of tactile devices such as exciters and bass shakers can provide? If so, I would strongly recommend a formed aluminum (Butler Built, Kirkey, Ultrashield), fiberglass or carbon fiber seat as opposed to a tubular seat. The reasonably priced NRG Prisma fiberglass shell seat is getting very good reviews from within the sim racing community, while bigger names offer non-FIA spec seats at prices significsntly cheaper than their full-on FIA racing sests. Look at Cobra, Corbeau, Momo, OMP, Racetech (great but pricey seat from NZ!), Sabelt, Sparco, etc..
Solid shell seats of metal or fiberglass/composite enable the placement of multiple exciter units using 3M VHB adhesive to transfer various engine, road/track surface, and other effects to different regions of the body.
3) Do you foresee yourself moving (sorry for the pun) to a motion system? If so, consider a seat which will enable attachment of a 4-, 5- or even 6-point racing harness to add to the immersion factor and perhaps add some safety for extreme motion settings. You likely won't need the 5-point belt to prevent submarining in even the most violent sim racing accident, but a 6-pt harness would be more comfortable for a male wanting to go the full anti-submarine route. Harnesses can even be fitted to a tensioner system which can really deepen immersion.
Good luck & Godspeed!