Well i just got a phone call from my mechanic whose putting in my 350 and he is saying that my car has a newer style 305 engine, and the 450 i bought is an older styler with a 2 piece rear bolt set or some bs like that and mne is a 1 bolt set.

 

Ok, why don't you take the time and fill in your car info in the sidebar so we have some idea about what car you have.
What's in the engine bay now? 305 TPI? 305 TBI?? Your 2 piece rear mean seal 350 will bolt up just fine, you'll just need the right flexplate or flywheel, and the right starter.

If your mechanic phoned you to tell you that a 350 "won't bolt up" and then hung up without telling you what HE will need to do to fix your problem, i'd be looking for another "mechanic".

 

OK, so i geuss i wasnt all there when he was talking to me (i was sleeping) but i called him again and this is what he told me. My 305 is a neweer block then the 350 and its balanced at the flywheel where as my 350 is an older block hat is balanced at the crankshaft. and also i'll need a new starter. he said that if he were to get it running it would vibrate like crazy. now is that normal?

 

Yea, I mentioned that up there.
1 piece RMS is the new style.
Your 350 is the older style, 2 piece RMS.

That's correct, you will need a 2 piece RMS flywheel or flexplate, depending on if you've got the auto or manual (and a pilot bearing if you're using a manual tranny), and you should be able to use the 305 starter on the 350.
The 350 might need to have a hole drilled to mount the 305 starter.

You can't use a 168 tooth flywheel in this car, it won't fit in the bellhousing, so you need a 153 tooth flywheel (or flexplate) and the starter to match it. The 153 tooth flywheel on your 305 won't work because it's made for a 1 piece RMS, so you have to buy a new one, like one for a 1982 camaro for example.

 

No, both are balanced at the crank.

No it won't. He doesn't have the first clue about balancing.

It couldn't possibly make a lick of difference how your 305 was balanced anyway, because you're not reusing any part of its rotating assembly.

 

ok cool, my mechanic ended up finding a flywheel that is gonna work, hes just now worried cuz he said its gonna vibrate, and im wondering if this vibrating is gonna be anything significant or if its just routine for everyone?

 

If it's the 153 tooth 2 piece RMS internal balance flywheel, then it's fine. It'll only vibrate as much as the 350 engine did before you put on the flywheel.

 

It's not going to vibrate unless whoever built the 350 is as ignorant as your "mechanic".