For what it's worth, the Stanadyne FM100 filter base is a pretty good candidate for the spin on conversion. What makes it even better is that there was a major dump of WIX elements for that base a while back. Gimpyrobb has over a thousand of them. I'm switching all of my trucks over to that base solely as an economic issue. I can buy a lifetime supply of filters for the cost of maybe 12 box filters and the bases are in the $50 range. You can add heaters and water sensors and all kinds of stuff to these bases. There have been more than a few folks who have done the switch right here on Steel Soldiers.