This and...
this.
These are both good suggestions. However, to really answer the question, all I can do is respond with the following question:
Why are you recruiting a fullback?
It's not sarcastic or rhetorical. But every time you're recruiting a player at every position, it's a question you need to ask yourself.
Why am I recruiting this position? What are the expectations for players in this position in my offensive system?
Fact of the matter is, every playbook has Goal Line formation in it. Therefore, every playbook has a fullback in it, and therefore when you look at recruiting needs, you're going to see that you need a fullback.
If this is the only formation in your playbook that you use that needs a fullback, then honestly, don't waste time recruiting a fullback. Furthermore, don't waste time recruiting a guy who even remotely resembles a fullback. Recruit a couple extra linemen and plug one of them in for formation subs on your goal line set. He's going to be a far, far blocker than any fullback, athlete, runningback, tight end, whatever you find to put in that spot that you think will make a good fullback. And don't change his position... leave him as a guard or center (if he's a tackle, change his position to guard/center, or better yet, just try picking a guard/center).
On the completely opposite end of the spectrum, if you're running a triple option offense and you need a versatile fullback who is more than capable of running the ball, you want to look for strong, oversized power running backs. Think of a Peyton Hillis type. He played Fullback for four years at Arkansas and now he plays running back for Cleveland and is on the cover of Madden.
Lastly, suppose your a pass-heavy, shotgun heavy spread offense. You've got some of those shotgun formations with the HB and FB standing next to the quarterback. For this FB slot, I highly suggest simply recruiting extra speed/balance HBs, identical to the HB you have in the actual HB position. And keep in mind you can use hot routes to audible either back into or out of passblocking duties.
But for the vast majority of everyone else who runs the I Form at least a good 10% of the time, you most likely want to find an undersized TE. This will give you the best balance between blocking ability and catching ability that most offenses will use their TE for.
Personally, I am always going after the bigger power running backs for my offense. I don't run triple option, but rather a run-heavy pro-style offense. I hand the ball off to my fullback a lot, both on called FB runs as well as triple options out of the I-Form.