Long post but need help with 1952 Chevy 3600 build.

I have been back and forth on many aspects of this build during planning.  I have finally decided to keep the original chassis and go from there.  I now have the back half of the body pulled off of the frame.  I am trying to find out the capabilities of the original rear end.  Would it be more feasible to re gear the rear end or swap in a later rear end?  My plan for this truck is to swap the 216 with '02 or newer vortec 4200 inline 6 mated to a 5 spd manual tranny.  Would the original rear end stand up with this combo?  Unmodified this engine makes 270HP so I just need to know which direction to head with this rear end before starting my search for an MII IFS.  Also where do I look for lowering blocks?  Any help would be great.  Thank you for being patient with me.

-Greg  

I'd start by figuring out what gear ratio you have now, and the overdrive ratio of the 5-speed.

If you have the axle I think you have, You are somewhere between 4.11 and 5.47. If you have 4.11, you should be o.k., if you run fairly tall tires.  Otherwise, check out any 67-72 3/4tons you find.  Some came with 3.90, some are posi-track. The one in my 62 is both.

As far as capability, I put a 402 in front of mine, then made 11 passes in 2 days at the SCRA dragstrip, in Great Bend.  
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1949 Chevy 1 1/2ton, home-built hydraulic wrecker.  Rustoleum industrial black, with flames.  Flamethrowers out 5" dual stacks.
1962 Chevy C-20, 402BB, 4-speed, 3.90 positrack. Hauls my camper.... among other things.

Forgot to mention, that you won't need the whole 67-up axle, just the pumpkin.  From what I found out, they are interchangeable from 47-72.  
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1949 Chevy 1 1/2ton, home-built hydraulic wrecker.  Rustoleum industrial black, with flames.  Flamethrowers out 5" dual stacks.
1962 Chevy C-20, 402BB, 4-speed, 3.90 positrack. Hauls my camper.... among other things.

That is correct, you can pull the axles and just switch out the 3rd member.  I found that most AD series 3600 came with 5.13:1  While most 69-72s I looked at had 4.10:1's.   An interesting approach is look for a 3/4 ton truck box made into a trailer.. you can buy it, switch out the pumpkins and re sell it for no money loss.

Question I have for you tho is.. what bolt pattern wheels are you planning to run? Most disc brake kits made for IFS are for  5 or 6 lugs not 8.  
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1950 Chevy 3600

1942 Ford Jeep

Well that's another thing I'm investigating.  All in all I want a good gear set on the rear, also disc brakes are a must.  Not sure of the bolt pattern yet since I'm still not sure about the front end. It will be a MII IFS most likely and I believe those have a 5 bolt pattern.  Are there disc conversion kits out there that will fit?  I'm sure a disc conversion would also allow me to pick the bolt pattern I want or am I wrong?  

Yes, Front is not a problem,  I like the CPP selection, but know of others who used Brothers and Ecklers classic Chevy to purchase their disc conversion.  The reason I asked about the number of lugs for the rear is I have not seen a disc conversion on a 3600 full floating rear axle (8 lugs). Most brake kits on the rear tie into the outer flange where the drum backing plate mounts. And even if you decide to run drums on the rear I assume you want the rear wheels to match the front (or maybe not.) Have you considered a 9 inch Ford conversion?  
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1950 Chevy 3600

1942 Ford Jeep

I have considered it but I have been unable to find one in the junk yards out here.  I'm trying to find most of my parts at junk yards to save a bit on cost.  I think the only thing I will be buying new is the IFS.  I'm really thinking about finding a 60's to 70's pickup and grabbing the tranny,shaft, rear end and rear suspension.  Basically something I could bolt up to my 52 frame with little mods and will bolt up to a 292 L6.  BTW I do want the wheels to match.