I bought a 305 for one of my 86's that I am going to restore to replace the horrible catastrophe of a 350 swap that was done by a previous owner.

The 305 was from an 87, so unfortunately it isn't correct, but still closer than the 350 in it. The weird thing is, the intake on the 305 has an odd thermostat housing bolt pattern that I have never seen on a SBC.

After pulling the OE thermostat off the 350 to drop on it, I found out the bolt holes are not spaced the same as every other SBC I have ever worked on. I checked all the other intakes I have laying around at the house, and they all measure a 3-1/4" bolt spacing center to center. This intake has holes drilled on center at 3-1/8" inch.

I check Rock Auto and the 86 and 87 T/A's have the same part number for thermostat housing.

So, what's up with this oddball intake?

 

Weird.

Post pic of intake.

 

Here is the best I could do without removing the carb.