Dodge: Engine doesnt heat up, engine temp, dodge dakota

Question
Since I read your response I did a little research on line regarding rodding out.  Half the time they say it works(especially as related to overheating) and the other half state that rodding causes damage to the tubes.  My question is:  Since I plan to run this truck into the ground, only has 63,500 miles, and the body is in excellent condition, I can see my owning this for another 5 years - would it be just as wise to replace the radiator rather than just rodding out?
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Followup To
Question -
My 1999 Dodge Dakota's engine doesn't heat up - not a problem with overheating, one of underheating.  As a result, I have no heat in the truck to speak of.  The thermostat was replaced 2 months ago or so.  Then replaced again last week with Dodge thermostat.  My mechanic stated that no matter how hard he tried he could not get the engine temp greater than 200.  The guage on my truck doesn't even register 200.  He can't figure out the problem.  Let it run 40 minutes, no heat.  Put blanket over radiator to decrease cold air coming in - no luck.  Why won't the truck heat up?
Answer -
The radiator is more than likely the problem,has he tried rodding the radiator out?Insufficient antifreeze can also cause this.

Answer
Maegan,
Yes it would be just as wise because radiators now can be ordered online for a fraction of the cost as you would pay for one at the autoparts store.I think i got mine from radiators.com.It was ordered for a tahoe original price was $380.00 before taxes.I ordered it from them for $175.00 and they shipped it for free.So yes it would be better i just hope this is the problem.Does the radiator have any kind of white looking debris or build up in it?