Tire question, can I replace a 103 load rating with a 101 rating?

Short answer: NO!
Long answer: Tire load rating for maximum load per tire.
Load Index 101 = 1819lbs (825kg) per tire Speed Rating “T” = 118mph
Load Index 103 = 1929lbs (875kg) per tire Speed Rating “T” = 118mph
Example—- Odyssey weight is about 4500, capacity is for 8 people at 200 pounds each total is 6100.
So the math sez 1550 pounds each tire. Normal maximum load.
Math answer is maybe, but you should not use a lower rated tire, becuz you could end upside down on the side of the road with a blow-out.

You may think from looking at the numbers that you would be find, especially since there are two tires at each end and therefore 3638lbs(1650kg) capacity at each end, and you’d be right…. if you never moved.

However, if you take a corner, the outside tires take more weight due to weigh transfer, just as hitting the brakes puts more weight on the front tires. Therefore, 101s would be a little risky unless you run the van nearly empty (no cargo, no more than one passenger) and if you drive the way I drive then it’d be a blowout waiting to happen.