If it's been hard to pull the shifter out of reverse, try loosening the side-cover bolts and tapping the side-cover upwards; it won't move much, only takes a few thou. Then re-tighten the bolts. Just a tad too low creates an interference that will jam 1st/2nd gear but will allow 3rd/4th.
Put a large crescent wrench on the bottom of the forward trans lever and pull the it rearward to un-jam it.