Wix listing for the Kubota tractors is generally sound, but there are some interesting "hmmmmmmm ...." filters.
For example, the L3130 takes the 51311.
The L3240 (the updated series of the L3130) takes the 51307.
My L3430 takes either the 51311 or 51307 (they actually list both).
There are some minor differences between those two filters; the BP value is separated, the 51307 is a tad longer, etc. But overall they both work fine in the Grand L series. Generally, because both are listed for mine, I'd have to say that it's likely that either filter will fill the bill for all those Grand L series (both the 30 series and 40 series), but as I am always of fan of understanding risks, you would be best advised to stick to the filter maker recommendation.
It's important to note that the BP pressure setting does not really come into play that often anyway. While not a direct comparison, we can draw some fair conclusions from Jim Allen's BP testing he did on his truck. The BP valve RARELY opens ever, and the only times he could get it to burp open was quick, high-revving blips of the throttle with cold oil that was thicker that his vehicle spec (running 10w-30 instead of 5w-20). Other than that, the BP valve never opened. BP events are RARE in most any application. The BP does protect the media in two circumstances:
1) cold starts with high dP during high rpm
2) blinded media
Most any BITOGer will NEVER, EVER get into either situation. Most of us are smart enough to not flog a cold engine, and there isn't a member here I am aware of that would EVER leave a filter on too long (although many waste filters and pull them prematurely ... but that's a difference vice I have for a different day ....)
As noted by others, there isn't a small diesel compact tractor out there that has been known to die an early death due to filter brand selection. Nor oil brand selection for that matter. As long as one uses a properly spec'd product for the application, anything will do quite well. There is really no way (discounting the existence of flaming opinions as evidenced here in this thread) which filter or lube is "best", but there are a LOT of great products from various brands that will help that Kubie last WAY, WAY past any use you'll have for it.