The side feeds can be run higher duty, they are a later design.
Do you have an RB20, RB25 or RB26?
The kit is only necessary on the RB25 as they are the only side feed.
RB20 and RB26 are top feed, I can get direct fit. Only difference is impedance, RB20 is high and RB26 are low. I usually can either low or high but don't have any right now.
Send me a PM with your email. Let me know what you need, I will let you know when I have some.