Re: 86 85 hp force
If the two bolts you are describing are one on each side and go straight up into the front cover that mounts the kingpin, then they are upper motor mount bolts. They are usually 3/8 bolts with a 9/16 head but I have seen some 1/2 with a 3/4 inch head.
If they are 9/16 head, they corrode and rust because they are not stainless and the heads round off. They become too small for a 9/16 to grab and there is not enough room to get a gripping pliers on them. They are tight but the corrosion is usually limited to the heads and they are usually not stuck in the motor mount.
I have had some luck by hammering on a six point 13-14 mm metric socket and turning them off. You run the risk of splitting the socket though.
Sears makes a socket type tool set meant to remove rounded-off heads. I haven't tried them yet but they will be my next tool acquisition.
Since these screws go into the rubber motor mount end plate, and since you do not want to restrict the rubber biscuit movement, they are only about 5/8 inch long. Even though stainless is not as strong as grade 8 steel bolts, it is acceptable here because there is an engine stop on the rear of the head which limits engine movement under hard acceleration. So, it is unlikely that the engine would move enough to over-stress these bolts.
However: If you want to feel safer, drill and tap the motor mounts for 1/2 inch bolts. To avoid future problems use anti-seize on the threads.
The other side of the motor mounts are bolted into a square hole in the midleg with two bolts inside the engine block mounting plate. If you are going to remove the engine block, these mounts are held in place with two steel spring washers (bolted down) each side and they rust. Again--if you are removing the block, replace these steel washers with Extra Thick Stainless Fender Washers. You should be able to find them at Fastenal; you will need to grind down the diameter a bit to make them fit, but then you will have an indesructible mount. If you do not want to replace them, coat them really well with silicone rubber RTV.
