Converting...or attempting to convert from the th-350 to a 4 speed. I have
heard that there are 2 different types of bellhousings 10.5 and an 11. It is a
454 big block and has the 168 tooth flywheel, what is the correct bellhousing
I need, don't want to accidently get the wrong one, have heard the truck
bellhousing wont work and how can I tell the difference between the 2? thanks for the help

http://cgi.ebay.com/ebaymotors/GM-SBC-BBC-3899621-11-Aluminum-Bellhousing-Cover_W0QQitemZ4612987966QQcategoryZ34208QQssPageN ameZWDVWQQrdZ1QQcmdZViewItem


or a lakewood

I would go with a lakewood.

But how can I tell the difference between the 11 in truck bellhousing and the
11 in performance bellhousing like I need?

Matty,
Somewhere on this planet are pictures of a car and a truck housing for comparrison, but I don't know where to locate them. Maybe someone will find the pictures and post them.
So, for lack of pictures, I'll describe the diffeences as best as I can. Someone included an Ebay link for the car housing. Notice that the lower portion of the housing is just rounded. A truck housing has an additional bulge around the lower portion of the housing. Once you see one, you will NEVER mistake the truck housing. Also, the car housings have a 4 5/8in hole while the truck housing has a 5 1/8in hole. THIS HOLE IS THE CRITICAL PART!!!! The truck housing will completely bolt up to the engine, fit over the 168 tooth flywheel and the tranny will bolt up to the truck housing. BUUUUUUUUUUUUUUUUUUT, that hole is what properly centers the tranny with the rear of the crankshaft (critical). YOU CANNOT DEPEND ON THE FOUR BOLTS THAT ATTACHES THE TRANNY TO THE REAR OF THE HOUSING TO PROVIDE PROPER CENTERING OF THE TRANNY!!!!!!!!!!!!!!! Now, there is someone here who makes an adapter ring to allow installation of a tranny (such as a Muncie) on the truck housing. But, even though that would work just fine, the aesthetic results are kind of ugly because of that big additional bulge on the bottom of the truck housing.
The housings are NOT for 10 1/5in and 11in flywheels!!! Those are the sizes of the 2 different size clutches. The flywheels are 14in with 168 teeth and 13in (some say 12 3/4in) with 153 teeth. Take a look at that Ebay flywheel. Notice that the bulge for the starter nose sticks out from the side about 1in. That's the BIG housing. The smaller housing has that bulge EVEN with the side of the housing. There are casting numbers to look for on the big housings, BUT, just looking at the position of the bulge for the starter nose will IMMEDIATELY tell you if the housing is big or small. The casting numbers for the big housings are:3899621, 3872444 and 464697. The 697 was a later housing as well as a service replacement housing from the parts dept. The 621 is the most common housing used on Chevelles, but either of the above 3 casting numbers will totally interchange and work perfect.

And, some added info. Since you have a 454, you need to know (just in case you don't know) that a 454 requires an UNbalanced or EXternal balance flywheel. That means that a flywheel for a 454 (as well as the SB400) has an additional weight cast into it on the side facing the engine. All other flywheels are NEUTRAL balance. Also, you will need to use a starter with the staggered bolt pattern and a CAST IRON nose (the alum nose with a staggered bolt pattern is too big to fit into the bulge of the housing).
Hope this helps.

That helps alot, thanks for going in depth to explain, now I understand.
Again thanks for taking the time to break it down. I didn't even know about
the starter issue either. With that new found knowledge my search for the
correct housing begins...