These units are not really within the site's specialty, but many of our members have tractors like these from different manufacturers, many makes and models. So I googled Springfield 36
. It is clear that these are somewhat rare and finding another one in decent shape is going to be difficult. Finding one in restored shape may prove to be more difficult.
There is a thread here on the forum that mentions one of the Springfields 36's went for a pretty penny - Springfield 36 Garden Tractor
I have no clue what it would be worth for insurance purposes. Hopefully David will pipe in on this or you could send him a PM from within that thread.
Knowing what the hp of the 36 is would help as well. The early ones were very low hp models and the later ones were somewhat larger. To get a current price will be impossible. Replacement value would have to be somewhere around a mid-range lawn tractor however these new ones are not built in the same manner and are far less likely to last 10 years never mind 40 or more. That is one of the problems when an older unit is lost to fire etc...