Hello George,
Personally, I wouldn't.
There are MGR specificationss for wheel rims and the tyres that should be fitted on them, so moving outside these combinations would likely invalidate any insurance claim you may have later on. Here's the 1999 Handbook'a info on sizes.
The 205/65-15s will certainly fit the existing rims, but will have an impact the speedo accuracy. The tyres could eventually suffer circumpherential cracking around the tread (been there-did that myself in the '60s !).
TC