Ok-decided to go shroud route verses electric fan But....help!

[ubtripn]

I listened to what all had to say and decided to go with a fan shroud to cover overheating while in heavy traffic. But my fan is 19 inches and I believe the LMC shroud is 18 inches. (Which I now have.) I can buy another fan (not flex) but the 18 inch says for use only up to 250 cid. Even LMC does not sell an 18 inch fan which makes no sense because the truck came stock with a 327 and now has a crate 350 so shouldn't 18 inch be right?

I am clearly missing something and need some advice, thanks everybidy.