I installed the Inferno Heater with the Seizmik soft doors on my HD8. The installation was super simple. Heats up within minutes with great toasty warm heat.
Have you considered the Seizmik soft doors? I found a lightly used set on Craigslist for $600. I think they retail for $1000 here in the USA. Lifetime warranty. I live in Vermont and they have been great for keeping out the worst of the cold while plowing snow. I'll be adding an Inferno heater...
I picked up this 7X14 Alcom Stealth aluminum trailer which has a 84" interior height for $6200 in April just when Covid was making things hard to get. The price has since jumped to $8500...Ouch!
I plowed snow for the first time recently with my HD8. It exceeded my expectations. Yes, I agree that the $3500 difference wasn't worth the extra 200 cc's.