Similar to Kevin you can review my project photos and questions/comments.
Once you have the door openings correct and braced you can move the bulk of the cab around as needed to get it level. Starting with the floor/firewall get the front cab mount area repaired. Depending on the integrity of your door hinge post and rocker panel you may be able to cut away the inner and outer cowl panels to provide access without loosing your hinge post location. There are a lot of interacting pieces in the rocker panel, door hinge post, inner cowl, inner-to-outer cowl, and outer cowl panels. A lot of those interactions may not be obvious depending on how much of the material has disappeared over the years.
If you can post pictures it would help everyone here provide more specific information regarding your specific circumstances.
