Just a quick check, is the oil level being checked with the engine warmed up and RUNNING. With the engine off the oil level will not show on the dipstick. It should be not be filled over the halfway point on the dipstick. When the ppi is done make sure he checks the headstuds. 2.7 with soft mag case may have pulled studs.
It sounds like the engine was swapped in 1980 for a 2.7. There are 2 numbers on the engine to the right of the fan housing. One is the serial number and the second is the engine type. If it was a new replacement 2.7 it might not have a serial number, but it will have an engine type number.
Bubbling paint means there is a good amount of rust underneath. Sounds like it was quickly repainted to cover rust instead of repairing it. Suspension pan, battery boxes, rockers are places to poke with a screwdriver for rust. A quick check of the rockers would be to use the factory jack to try and raise the car. If the jack points bend they are shot. A lot lf times the undercoating and paint can look good, but underneath the metal is rusting.
This car looked good on the outside but if you read the thread you get an idea what can be underneath.
http://forums.pelicanparts.com/paint-bodywork-discussion-forum/545166-restoration-my-69-911-a.html
If it has a solid body and engine passes ppi it could be a fun car. If it has a lot of hidden rust, or the engine needs work $20,000. can disapear quickly. It's one of the reasons some cars sit in the garage, too expensive to repair.