1968 chevy c-10 question about stock motor size

hey everyone, i just picked up a 1968 chevy im guess its a c-10 it says custom onthe doors, the truck came with a running inline six with a 4speed with granny low, my question is how can i tell what size is the motor? is there anything on theblock or head? i need to find what size cuz didnt chevy make a few different sizes? and is there any sites to order custom/after market parts for the motor. sorry for all the questions noob here.  

Anyone?  

It's either a 230, 250, or a 293. I have a '73 C-10 with a 250 inline six. The 230 had different rocker arms, they couldn't be adjusted the conventional way. Since you've got a truck, you are more likely to have a 250 or a 293, as the 230 was mostly used in cars and the older trucks of the '40s, and was phased out in the late 60's. If you have a 250 motor, I can tell you that you have a very good motor, as my truck has over 100 000 miles on it, and the motor is still running fine! GMC even used them in their school busses of the 1960's because they yould start in cold weather easily and had lots of torque when hitched to a 4-5 speed tranny. They only have a single barrel carb, so you get relatively good gas mileage, up to about 22-24 miles per gallon.
I hope this has been some help, if not, take your serial number and go to the nearest chevy dealer. They can probably look up the serial in their database, and they should be able to tell you what motor your truck came with, providing the motor wasn't swapped.  

are the parts the same for the 250 and 293? as far as tune up plugs wires cap rotor? i wan to get this but dont know the motor size also it looks like it has smog system on it it has the pump and has a pipe that runs from the pump to the head then looks like it breaks off to each cyclender the pump isnt hooked up so i wanna take all that stuff off would i have to plug the holes from the pipe that go in to the head?  

THE 68 NUMBERS ARE ON THE PAD RIGHT SIDE OF ENGINE AT THE REAR OF THE DIST. THE 250 IDENTIFICATION CODES ARE TA,PF,TE,TT,PV,PW,TF,TC,TD,PX,PC
THE 292 IS UH,UT,UP,UO,U3,UM,UQ,UR,UN  

the only numbers on the block are con2    m15   328575 gm 82