58-64 frames were all pretty much the same ("drop seat" frames) 65 was it's own animal as it was the first year electric start frame. The 65-69 frames are also pretty much the same. A 65 frame seems to bring the most coin as it's a one year only pan item (though 66-69 generator shovel frames are near identical) Some years had key locks, some did not. Some years had slightly different brackets and some other subtle changes. In good shape and not cut up at all- frame and round swing arms are in the $1200-1500 range in my area. On the back down tube castings there will be a series of numbers with a "-58" at the end. There is also a date code stamped on the top motor mount. If you can post the number stamped there I can tell you the year. Be SURE to get a good look at the neck area and see if there's evidence of any work done there. I have seen MANY post '70 frames that have been doctored to look like earlier, no number frames. A dead give away is the rear down tube casting numbers and passenger peg bracket shape/location.
Hope that helps.