I actually still have several slide-rules tucked in a drawer somewhere!
.... but you won't need it, cuz as noted above - it's the total weight of 914 + dolly or trailer that you're towing & tongue weight is usually about 10-15% of that total. I went through this recently for my wife's recently acquired restored vntage travel trailer, so it's more than I ever wanted to know!
It's probably a 4 cyl small SUV, unless it's the braked vs non-braked weights.
If you're okay to tow 3000 braked, then you'll need a 700 lb braked trailer + 2270 lbs of 914 with drivetrain (much less if engine/transaxle is out of it), or else & more likely a braked dolly.
You may be better off renting a pickup to tow with, from U-Haul, Hertz Equipment rentals, etc. Penske & Budget will rent you a big 16-20' box truck with a hitch too, but Penske only allows you to tow with their trailer (more rental fees) & not sure about Budget.
One other possibility is if you can find a Toyota Rent A Car (TRAC) participating dealership who actually rents an SUV or Pick-up to tow with (I found that most dealers don't).
The regular car rental places don't allow towing with their SUVs/trucks, even though many have tow set-ups.
Most of the above you can Google & find online, as well as some good towing safety info.
Good Luck!