Truck smokes on inclines
 

I figured after spending all weekend on here I would register and see what people thought.

I have a 1991 Toyota pickup with the 22RE engine in it. Right now there's around 142k miles on it. For the past few years sometimes when my family would launch a boat the truck would start smoking on the ramp. When I say smoking I mean smoking so bad that twice we've had the park rangers come running over and ask if our truck was on fired. I recently purchased the truck from my grandfather and we've been using it without any real issues besides the occasional puff of smoke when going up a steep incline. Now it seems like anytime I go up a hill smoke comes billowing out the exhaust.

Any ideas what the cause of this is and about how much it would cost to fix? I want to keep it alive if possible, but besides the engine smoking the radiator has a slow leak and the transmission makes noise in 3rd and 5th gear. At this point I'm not sure what's best.

What color is the smoke? Black, grey, white, blue? And it's only out the tail pipe right? And is this only under load or sitting idle on an incline as well?

White smoke. I've only tried it under load, never idling. I can test that tomorrow if none of my neighbors are around!

Only thing will make it smoke white is coolant (or water)

Most likely a blown head gasket. Possibly a cracked head or block.

Is it real thick white smoke? Still there well after the warm-up cycle? Any hint of a burnt coolant or "sweet" smell?

Few more things to add. I'll start it up later and try to get a video of it smoking up a hill.

The coolant leak is very slow and I can see it coming from the top of the radiator. The oil is low after it smokes. Maybe the smoke is blue, not white. There's a note from a Toyota dealership on a maintenance receipt that says it could be the valve seals, but they weren't sure (and it was 10 years ago). This happens when it's warmed up. I can't remember exactly how it smells, I will pay better attention today.

Valve seals on one of the back cylinders was my initial guess.
To me it sounds like oil is pooling in the back of the cylinder head and leaks into the cylinder on an incline. The fact your oil is low helps my suspicion too. Could a compression test help to confirm leaky valve guides?

compression test may or may not indicate a valve seal problem most likely not though, but a true leakdown test will.

this may sound stupid, but has the simplest thing been checked (PCV valve)? air filter clean?

PCV valve was clean as is the air filter. I replaced it 4 months ago (~1,500 miles ago). New cap, rotor, plugs and wires roughly a month ago as well.

How would one do a leakdown test?

I tried to get it to smoke before but didn't have time to get to a big enough hill. Will try again tomorrow.