Need advice for 99th percentile twins.

I’ve posted this in a couple other subs as well.

My twins are turning 2 in January. They are biiiig boys and we have them in the Graco Slimfit 3-in-1 currently. The rear-facing weight limit is 40 lbs and my slightly larger twin just hit 40 lbs. The other twin is 39 lbs. I am very uncomfortable with forward-facing them already, though it is legal in the state we live in.

Car seats are way out of our budget right considering we need to buy 2. I can swing it for one Graco Extend2Fit 3-in-1 at the moment, but definitely not for 2. My husband leans more toward forward-facing them because they have been gaining about 2 lbs every month consistently and the highest rear-facing weight limit I can find is 50 lbs. Essentially, he’s not convinced it would be worth it if they continue to gain weight at this rate because we’d end up at the same issue in a few months.

I guess I’m asking for opinions on whether or not I should go ahead and get the one car seat for the twin who is maxed out and try to come up with enough for a second seat before my other twin hits 40 lbs, or if it would be more reasonable to just turn the seats we have around. I’m just lost on what to do in this situation.