IBU's in John Bull hopped malt

I have a recipe that calls for john bull hopped dark malt which no longer exists. Does any one know what the IBU's is? I was thinking about adding 1 oz. fuggles of willamette pellets to the 60 min. boil... I am makeing the toad spit stout in papazians book with some changes.

I forgot to say my brewing supply store didn't have hopped muntons or i would have used that so i am using unhopped muntons

That should be a fine change. No idea what the original had, but an oz or two of a moderate AA% hop should give you enough bitterness (depending on what you are looking for).

If that is the recipe with the load of gypsum, leave it out.

Yes it has 8 tsp. ...I was thinking that was too much. there is a couple of things I am going to do different:

Papazian's Recipe:

3.3 lbs. John Bull hopped dark malt LME
4 lbs Dark DME
.75 lbs crystal malt
.33 lbs roasted barley
.33 lbs black patent
1.5 oz whole Northern brewer (60 min)
.5 oz whole Fuggles (10 min boil)
8 tsp gypsum
Irish ale yeast
.75 cups priming sugar
He only uses 1.5 gal of water to boil with (Im worried about scorching with that much malt)

Mine:
3.3 lbs unhopped muntons dark LME
4 lbs DME
.75 lbs crystal malt 120l
6 oz roasted barley
6 oz black patent
4 oz malto dextrin
1 oz Nothern Brewer pellet hops (60 min boil)
.5 oz willamette pellet hops (60 min)
.5 oz Fuggles pellets hops (10 min)
1 tsp gypsum
irish ale yeast wlp004
.75 cups priming sugar
and boil with 3 gallons of water

I dont want it to be over powering bitter, just enough to balance out the strong malt addition with a little bitter bite