1989 Jayco Sportster 8, Upgrade Recommendations

I would go with the Wave 8 Catalytic Heater. You can get them Wave 3 or 6 but the 8 is the big boy. They use no electricity but you could use a small 12 volt fan to move hot air into the cab over. They do not put the moisture in the air like a Buddy heater. Bunch of van life youtubers use them all the time and leave them on all night with a roof vent cracked a little but way safer than a Buddy heater imo