1990 Blazer Full Size 4x4 - Common Engine Problems/Maintenance?

[modasrar]

I have a 1990 Full Size Blazer 4x4 w/80K miles that I use for a plow truck. Normally it runs and drives fine, except that it burns about a quart of oil every 500 miles and the engine runs very unbalanced and shaky, though it runs strong, just shakes the truck at times.

Also, lately, after it's been running for about 40 min. the vehicle loses power and seems to almost want to stall out and I have to floor it to barely move but then the power will come back after I have turned it off, let it sit for a couple minutes and start it back up. It seems like some of the cylinders stop firing but I'm not sure.

Short of replacing the motor, is there any temporary or fast fix to atleast decrease the amount of oil the vehicle burns?

And what are some routine maintenance issues that I should look into that seem to be common problem areas for this vehicle?

I will be replacing spark plugs, air/fuel filter, spark plug wires and distributor. What else am I missing?