What is a standard wheel base for Dodge Ram 1991 Conversion Van B150 8 cylinder 109 127 or RAM VAN MAXI?

There isn't a single "standard" wheelbase for a 1991 Dodge Ram B150 conversion van. The wheelbase varied depending on the specific model and configuration (e.g., whether it was a regular van, a longer "Maxi Van," or a custom conversion). You'll need to find the information on the vehicle's documentation (like the title or original window sticker) or the VIN number. The VIN will allow you to decode the vehicle specifications including the wheelbase length.