When I moved my rays into the 480 gallon setups, I had an ammonia spike. I believe this was largely due to the bio media drying out completely over the several hours it took to get then systems switched over.
My advice would be to test the water daily to make sure all is well. If you do get a spike, daily 25 to 50 percent water changes should keep the rays alive. I did 50% changes daily (sometimes twice daily) for a few weeks till things got back to normal. Didn't loose a single ray.
The 375 will be awesome. Congrats and good luck.
Pat