i have a 86 cutlass supreme with the 307 with a four barrel on it. i've heard that the 403 is exactly the same just bigger bore size and different heads. im just wondering if this is true and how hard it would be to make my 307 into a 403

 

You can easily swap in a 403 but I don't believe you can make your 307 into a 403, at least not in a cost effective manner.

 

All SBO and BBO are EXACTLY the same on the outside, the BBO's are a little bit wider and taller, but anything with an Olds motor in it, will be an easy swap for a different Olds motor.

 

That is what I am doing also. Got the 403 from Mondello. 455 will fit as well but did not go that way. S l o w l y building engine really want to keep it stock as long as possible.

 

Welcome to CO. Many engine swaps have been made and you should not have much trouble. Members can help you out when the time comes.

 

I have 2 rulers exactly the same. One is 12 inches long the other is 13 inches long.
I realize what you are saying but to someone who is new to the concept or just browsing the forum they may get the wrong idea. Wording is the key to correct info.

 

[QUOTE=InfoJunkie;230594][quote=Redog;230427]EXACTLY the same on the outside, the BBO's are a little bit wider and taller, Glad to see that someone is filling in as the designated smart-a$$ in my absence.

 

I had noticed no post from you. Thought maybe you had given up.

 

Meh, you're right. I just don't want to see this guy go buy a 455 intake manifold and try to put it on his 350