NUWATC Rookie

well ive only had a Heavy in the tower pattern once, and we did have GCA finals going on, radar doesnt know what i have in the tower pattern. so im kinda wondering how to work it if the situation arises again. that time i got lucky and i was able to have the heave follow the GCA each time. i just cant think of a way to get the mileage for the aircraft on final from my heavy. essecialy if the GCA's are spaced 3 miles apart. I was thinking visual might be an out but i cant think of a way to apply it, and if i needed mileage and my radar display went out ( and it has ) i would have no way of doing so.