Engine guys

[slamin81]

what size  is this engine im thinking 305 not 100% tho. it in a 84 GMC SB

[DWFarmboy]

Dipstick on the passenger side usually is a give away to a 305 on older models.

Look behind the head on the driver side for the casting number on the block. Should end with 010 if its a 350.

[onelow84]

pass side dipstick just indicates that it is 81 and newer, get the numbers behind the drivers side head if you can...

[DWFarmboy]

Ok well from late 75 to 80 you could tell cause the the dipstick was on the passenger side. 

[bake74]

     You can not tell 100% for sure from just looking at a 305 or a 350.  You have to get the casting number from below the drivers side head on the block and run it to see what engine family it is from.

[1980c10]

     You can not tell 100% for sure from just looking at a 305 or a 350.  You have to get the casting number from below the drivers side head on the block and run it to see what engine family it is from.

Do this to be sure, too many variables any other way. Someone has done a few things on that engine as well. I see headers, carb, intake. it would be worthwhile to know what heads you have as well. For that look for a number as well under the valve covers or look for the pattern in the end of the head.

[Blazin]

The numbers on the blocks deck just ahead of the right side head under the alternator will tell you allot more.