My son has a 1996 Dodge Ram 1500 extended cab Pickup Truck.
I'm looking at installing the following:

Alpine 9813 HU
Infinity Kappa 692.5I 6" x 9" front
Infinity Kappa 52.5I 5.25" rear
Infinity Basslink 10" woofer w/amp built in under rear fold down seat

The problem I have is Crutchfield says the speakers will not fit in place of the OEM.
Infinity says it will
Cartoys says it will
Tweeter says it will

Who should I believe? I want to order online to save money but, I'm afraid it might not fit when it arrives. What other items should I get ie: wire harness, adapters, faceplates, etc.

Also, will these items work well together? Are these system choices good or bad?

Any help will be very much appreciated.