You can try, but I don't think it will work properly. It may work for some cogs, but even if fine-tuned around the middle cog, indexing may not be precise at the outer cogs. As tugrul said, the actuation ratio is probably different between that Deore and more modern RDs designed for 8-speed spacing.

As for the jockey wheels, that's not what's going to make or break whether it works. Most Shimano RDs made from the mid-80s onward have a "centeron" guide pulley which has some lateral free play, allowing it to sense chain tension and "auto-center" to a cog to compensate for imprecise index (or friction) shifting. They introduced this feature before they introduced indexing, it was one of the innovations that led up to it. Your Deore should have it (even the 1st gen XT in 1983 had it), and something with the word "centeron" should be embossed on the guide pulley.

If it doesn't work, shoot me a PM-- I have an 8-speed Deore LX long cage RD that I could trade ya.