I have a big block in my 55 Cameo. I did the swap back in 1970, but remember the biggest issues.
Exhaust, The stock manifold will not clear the steering box and you will have to get headers for a big block into Chevelle or, if you can still find them, into 55-57 Chev. You will have to modify the pipes on cylinders 3 and 4 to clear the stock steering box. That is what I did and I was able to keep the lengths of the primaries the same. You can mount a Saginaw box forward, and that solves this problem but causes others such as drag link and steering arm.
There are two ways of mounting the engine, using the newer side mounts or the older stock truck mounts.
I used the classic early Chevy mounts, the front mounts will be in the 6 cylinder pads, the rear crossmember can be used, with no modification, if it is a standard tranny. If you are swapping in a Turbo 400 or 350, you will need to make a rear mount for the transmission. You will also ned to make some snubbers that take the weight of the engine at the original transmission mounts. This provides stability and supports the engine in the middle. ( It might sound crazy, but it has worked for me for the last 37 years. ) I used the stock rad and because I run synthetic oil, I have never had a cooling problem.
I am using the stock floor mounted pedals. when I had the 4 speed installed, I was easily able to modify the stock arrangement to work properly with the clutch.
I have made so many changes to the driveline, that I can't remember whether or not you will have to shorten the drive shaft. If I remember correctly, I don't think so. If you run a Turbo 400, you will either have to find a front universal to mount the large yoke on the tranny to the small yoke on the driveshaft. A trip to your local parts store will solve that problem. I went to Dana and found a small yoke that mounted on the back of the 400. A universal is less expensive and does the same job.
I have covered a lot here, if you have more questions, I'll do my best to answer them for you.
Bob
