I took the front suspension off my 74 Road Runner. The steering linkage knuckle arms on the car have part numbers 3402848; 3402849. When I look up the numbers in my 74 parts book it lists 3402850; 3402851 as the proper number for these parts. I've owned the car since 1977 and this is the FIRST time I have taken the suspension apart. Not saying it didn't happen before 1977, but....
The parts book I have is dated November 1974. The build date on my car is Nov 1973 and I've noticed that there are a number of notes in my 74 book for part number substitutions after Dec of 73. I've looked the numbers up on lightningjar and no go. Does anyone have a 73 book that they'd be willing to look up these numbers in to see if the 3402848 and 3402849 numbers are from 73? Thanks.

Lots of Mopar parts are like that.The casting/stamping/engineering number on the part is one digit off from the actual in print part number.When it comes to zinc/potmetal parts the numbers can be very different.For example, the 66 Dodge Polara/Monaco right front fender moulding has a casting number of 2579716 and its part number is 2807050.Usually Mopar part numbers are even for right side pieces and odd number for left but they don't stick 100% to that rule.Lots of mid 60's tail light lense part numbers are flipped so you have to be careful when identifying parts.

there is a fact of diff between 73s and 74s on front suspension and is the LCA use threated in ball joints to 73s, and pressed in Ball joints on 74s, making a diff LCA and Ball joint for these years

buts thats the only PHISICAL diff I can tell

My 73 parts book shows 3402 850-1.

Thanks burnt o matic and everyone else for your responses. I guess it is an engineering number that is one off the print part number. The car is stripped down now to just the unibody and the rear end and it is the first time I've come across a part number difference. Everything else has been spot on.