1988 F250 460 2wd Power Problems

I just bought this 64k miles F250 for use with a slide in camper. I found that on the flat it would run fine but put a hill in the way and It runs out of steam in O/D. Change down and it's OK but get the hill any steeper and it runs out of ooomph again. I get that "pinking" clattering sound when applying the power above about 2k rpm in either O/D or 4th, it probably will do the same in all the other gears as well but I haven't checked that.
If I push things when it's pinking there is power there but it can't be good for it.
I also noticed a metallic rattle when accelerating in all gears at around 1200rpm, This is like it whether the camper is on or not. I thought it might have been the heat sheilds on the exhaust as they were held tight with hose clamps but someone suggested it might be a Catalytic module falling apart and the 2 problems are related.

Are you sure the truck really doesn't have 164,000 miles on it? The odometer could read 64K but could have rolled over a couple times. Is the truck a five speed? I got a 91' F-150 with a 5.0 and a 5-speed and that metallic rattle in all the gears, i found, is normal, I think its our catalytic converters decaying internally.

check the timing it maybe over advanced. try giving it a good tune up also check the egr valve is closing all the way and when your going to haul something run 92 octane and not the cheap stuff

Thanks for the replies.
I was on 86 octane, it may well be the timing, I have to change the plugs & leads at the weekend so I'll look at that also.
I'll give the EGR the once over as well.
I think it's a low miles truck, it looks very nice and is in A1 condition apart from a few scratches and dents around the bed. The bench seats and floor mats usually fall apart on the high milers but this ones is like new.
It was owned by an old guy who used it to potter about with his 5th wheel and I am the 3rd owner.
The rattling noises are a pain, I guess if I don't find something that's hanging loose I'll have to look at the Cat and there is plenty of advise on here to "fix" those.