@BrianCF, You are a bit unlucky caught between light and heavy bells. What I strongly recommend is using one 45 and one 55. It is fairly common and even recommended as an option to have uneven bells. I am finishing 1.2 with uneven bells. Switching bells after each set is a kind of micro wave that is welcome and motivating as you get to come back to your stronger arm (or strong and stronger as Pavel says) the next set.
An easy way to tell would be to test your RM with the pair of 45s. Especially, if it is over 12 then you can more clearly see your choices defined. I would let your RM dictate your approach as written in the program.
At 90 in the first week, I doubt that is going to produce the metabolic demand that is key to the program. It should be hard to stimulate adaptation. In contrast, the 8 RM would really be challenging especially in Giant 1.1. Of course, both would work. I am just saying that to get the most out of the program uneven bells would likely be the way to go.
Give the uneven bells a try and tell us how it goes.