I do not know anything about this alloy specifically (a necessary premise), but this alloy family is quite common (this one seems to take advantage of technologies from some of the old European high carbon 12 chromes and the newer V enhanced CrMo alloys-just guessing) and some general suggestions seem clear.
Preheat, IMO, will be a must and probably in the range of 450 or 500 degF. You have a high carbon alloy and high vanadium as well.
I would also assume you will need to impose an interpass regime with max's and min's because CrMo alloys with V are usually intended to provide a tempered martensite microstructure. Meaning you have to let it cool to below Ms and near Mf (these two transformations will determine where your PH and IP should fall-and I'm guessing you will have a very narrow window-high to slow cooling and prevent cracking, low to allow martensitic transformation) in order to allow multi pass regime to assist in tempering, as well as contribute to forming the V carbides which are probably important to the microstructure.
PWHT will also most likely be a must as well. Your HAZ will be a rock.
But keep in mind that these suggestions are just that (wishing to emphasize my original proviso). And are intended not as recommendations but as possible issues to take a look at.