there was some sludge issues on the earlier 4.7s due to a poor PCV design, combustion moisture would build up and milk up the oil on them, but I think that problem was only on the first couple of years. I've got an 04 Dakota quad cab that I bought with 30K miles, it now has 47K and have had no issues with the 4.7 in it. prior to this dakota I had an 05 Durango with the 4.7, and we put 60K miles on it with no problems other than the EGR valve failed at about 50K miles, and was not covered under the emissions warranty.

they're good reliable motors.

now, if you're planning on building one for power, you'd be better off at looking into a 5.9L swap cause that's a factory available engine those years, so it' drops right in, it's 80 cubic inches bigger, AND it's a lot cheaper to build.

or, look into a custom 5.7L hemi swap. again, more power easier to build.

there just isn't a lot of aftermarket support for the 4.7L some cams, headers, and that's about it.