Hey,
I'm your size (plus 6'5" and have biked for 40 years. It amazes small folk when we come to down hills and I warn them they will out coast me down the hill because I push so much wind. I have never been fast even in my 20's, but the racers I rode with on training rides were all amazed at my strength. It takes a lot of power to move a large frame. There have been tall folks in the TDF, but they are much lighter.
I have broken and/or worn out EVERY part on a bike except a fork. For some reason I have never broken one. I mean frames (steel, carbon and aluminum - I have broken two Cannondales and currently have a warranty replacement in my stable today), axles on wheels and pedals, every bearing bearing on a bike (including a Dura Ace rear wheel bearing I just wore out in 5000 miles, stems, bars, seats and seat posts, brake calipers and shifters - EVERYTHING. My most frequent victim for yeas was spokes and rims. Well into my 30's I always rode with extra spokes on every ride. I still ride with a complete spare tire, tube, tube patch kit and tire patch kit (in yester years I carried pieces of a sew-up tire to make tire patch. I have made and used a tire patch twice and numerous tires. I have rubbed rims down to past worn out by hard braking is less than a year. Imagine my glee when dual pivot breaks were born. I could wait till the bottom of long hills to break instead of braking all the way down because there was a stop sign at the bottom. BELIEVE ME WHEN I TELL YOU THE SMALL FOLK DO NOT UNDERSTAND WHAT IT MEANS TO BE OUR SIZE AND WHAT IT DOES TO THE EQUIPMENT. Even how a bike handles is different for us. Most manufacturers cannot make a bike that safely handles for us let alone that will last.
This modern stuff is much more durable. I can no longer bend or break an alloy seat post - a few years back I broke a carbon seat post - a frame edge at the top of the tube cut it after 3 months and it was gone.
Amazingly enough I have a wheel that I am still using after about 10,000 miles. It is an Ultegra rear hub with a Mavic Open Pro Ceramic hub. The hub is OK for durability, but I have gotten an unusual number of miles out of it for me. The rim just lasts and lasts. Sadly they are no longer made and the last couple of years the quality was poor.
A shop I have used for 15 years and knows my woes well has recommended the following to me: Mavic CX33 rim, DT Alpine III triple butted spokes and Phil Wood hubs. Their wheel builder has not yet had one of these rims fail for him. He knows I have used the Open Pro Ceramic and he likes these better for me. Get your wallet out though. I have a brother with a 30 year old Phil Wood hub. As a second choice his recommendation for me is DT350 hub, DT 14ga SS spokes and CX33 rims. I have one in the que waiting to be used.
Your front wheel does not need to be NEARLY as stout. Your do need to avoid the low spoke count, high tension wheels so popular today. I have one on my front that has lasted 4 years, so you can try one if it is one of the heavier ones.
Couple more helps: I have had zillions of flats from spoke holes and pinch flats from rim tape and tire edges. We need more tire pressure than the small folk just to keep the rim off the ground. On my Open Pro rims I custom fit and cut wood doweling into each spoke hole for all my wheels - not one pinch flat for years. You have to pick the rim take and rim and tire to match to get to work. I forgot to mention that I have had many tires simply "pull apart" while I am riding them. Amazing even to me. There are some tough tires out there now to choose from. Tire size: with the right tire, rim, tape, tube combo you can get away with riding a 25C (pressure needs to be at least 125 psi depending on the tire) rear and 23C front. 28C rear works in the rear and the pressure is less critical. Some bike portable pumps have difficulty getting very much over 100 psi when you are fixing a flat in the heat at the side of the road.
The above will get you a bullet proof wheel that will feel competitive compared to a full out touring hog. It is well worth the ride quality to try and get some performance. I have seen guys with performance wheels coast down hills faster than other guys on budget wheels can pedal and try and keep up. DO NOT go light - you could crash and burn big time.
Its a long note, but it took even longer to live though it to get to the information. Yes, I am probably as old as your grandpa. By the way , the only guys who are faster than me and my giant bike and wheels are small folk, and racers or former racers. It feels good.
S.