Almost forgot.....I don't know what you have for a driveshaft, but you don't want that to be your weakest link. An aftermarket unit would be much better than an OEM unit and I've had excellent results from Spicer solid u-joints in race applications. I don't know how well or long they will last with a lot of street driving & no way to add grease without disassembly. Otherwise, grease fittings in the cap may be preferable to ones with a fitting in the body between the caps. If using the fitting in the body, orient the u-joints so the torque will be applied towards the fitting as opposed to away from it - if that makes sense.