Case 644 K321 Engine mount History Question?

I would appreciate a bit of help knowing when Case began using what I will call a rubber mounted cradle to support the K321 in 644's. Our's is a 1972 644 with two-color paint scheme. I have not cross-referenced engine numbers as of yet, but believe the K321 to be original to the tractor. This engine is bolted to a panel welded between the frame rails and have only thick "rubber washers?" and bolts with locknuts holding it in place. There is no cradle as I see in pics of later 644's with single paint color - or for that matter, on Case 444's, 224's. Back in 2011 when I joined the forum, I was able to download the site manuals. They are somewhere .... my bad.
The reason for my question is that the K321 is in need of a rebuild or re-power. Life has taken a priority and the tractor has been on stands for almost 10 years. What began as a refurbishing to replace old leaking hydraulic lines, re-bushing too loose parts and rebuilding the starter generator system, when it came to the oil blowing engine, finances and life took over.
I toyed with the idea of an engine rebuild (pricey) verses a re-power using a sourced-good used engine. Two years ago I came across a K361Q in a complete '78 IH CC 1650 nearby and was affordable. (The tractor had been hand-fisted by the original owner, but is all there with many OEM extra parts.) I have read of the issues to anticipate of using an engine non-stock to the tractor. BTW, our 644 appears to be completely stock w/3 point minus the stock exhaust and judging by the wear on the clutch, the original included mower deck had been used extensively. Soooooooo ......
This is the basis of my question regarding what would be the original mounting system for a K321 in a '72 644. This engine vibrated because the rubber washers were squashed. We have a '73 IH CC 149 with the original K321 mounted the same way. And yes, the finger tips would tingle in short order there as well. Fabrication would not be an issue. I miss the 644. Life is still in the way, but having a dream these days would be good medicine.
Thank you in advance for any help. Be well, stay well one and all. M