Yes, I had to do this with mine, you need haeded paper from the garage, then it must say what the chassis no is make and model, engine size type etc withe the engine no.
Get it signed by the owner and send this with your v5 and a covering letter.
It took me ages to get this information from DVLA, about 6 attempts before they actually told me what the requirements were, they seeemed a little reluctant to go down in enegine size!
The owner may just give you a headed sheet with thier signature at the bottom to save them filling it out?