2old and MikeyMK are probably on to your best option...if one of your old Giants fits you well, go for a conversion!
I am another big, slightly damaged guy. I’ve gotten to know my ortho doc and podiatrist far too well over the past ten years. My bicycles are my favorite way to get some great, low impact exercise...and some fresh air.
I am 6’5” and 260lb, and most ebikes are not made for my size. I decided to convert an under utilized Cannondale Adventure 400 (jumbo frame) that my wife gave me sixteen years ago. Went to the lbs where it was purchased and had them convert it with a BaFang 750w mid drive motor...of my three bikes, it’s now my favorite. Every ride brings a smile. The front shock fork and shock in the seat post make for a comfortable ride, and the frame really provides a stable platform. The chain rings were replaced with a single 44, and I still use all eight remaining gears with the five PAS.
Upgraded the tires to Schwalbe Energizer Plus, added a new saddle, upgraded the brake pads, and it’s great. All for far less than the price if a new bike.
Good luck...I hope you find a worthwhile solution!
Last edited by Oldoarsman; 11-18-19 at 08:57 PM.
Reason: semantics corrected