I am finishing up my 1936 Chevy coupe in which I installed a Gen.III from a 2004 Tahoe. I am down to just a few lines left to install before I will paint and shove it off to the upholsters.. A few years back I did the research on what would work for my coolant system line routing, specifically the over flow tank. To give you a few specs:
1. Radiator was custom built by a fabricator that is known nationally, they have even built a few radiators for some of the popular car shows. I personally drew up the specs on my radiator for this fabricator.
2. The radiator highest fill point sits about 8" above the highest point of the heads (referring to steam lines)
3.. Exiting the radiator fill point at the cap is an overflow line, old style. While this was a custom built radiator which was not suppose to have a radiator cap or any opening for that matter (except a steam line connection) as to stay a closed system, it ended up with a filler cap and overflow connection. I returned this radiator 3 times because it didn't meet the specs of what I originally drew up for the radiator build. In the end I decided to work with what I had as I was worried about getting the radiator back when shipped off to this well know custom fabricator (fab work turned from 6 weeks to 6 months at this point).
4. On the pressure tank, there are 2 connections that exit the bottom in which I have brazed -AN4 male connections, no other connections exist. Top of the tank has a simple o-ring cap.

So, taking in mind that the heads steam lines aren't really needed as de-aeration should not be a problem when the radiator sits so high above the heads, will my coolant diagram work? I have seen this exact set up before on conversions but can't remember if they included or deleted the steam lines. In my original specs for the radiator they included a steam line port from the top of the radiator, so I set this build up for the steam line attachment in the way of plumbing the heads. I am hoping I can salvage this very expensive radiator with the current set up.

 

Forgot to ad diagram, geez, long dat

 

Very nice engine compartment. Would like to see where/how you mounted the coils. I usually put function over form so I'll just tell you what I did and let someone else talk about NEED for steam lines. On the '39 I drew up plans for what I wanted, contacted a national radiator supplier and they returned CAD drawings which I approved. Radiator fit the core support and mods hooked to the LSx as designed. I used an overflow like the one you have and added a sleeve in the middle of the upper radiator hose for the steam line to connect to. My thoughts on this is that GM saw a need to vent the probable steam pocket so the lines were added. There is a bit more "clutter" in my engine compartment but it runs cool.

 

33Willys can you send pics of your set up? Curious of what you have compared to what I am trying to do, any help would be appreciated! On the other LS based engine swaps I have done I always tried to keep the upper radiator level above the heads, which should eliminate the need for steam lines. I would really like to keep this a closed system. Originally I had plans to tap the back side of the water pump and plumb the steam line into a port at that location however, when the custom radiator did not work out as planned I have to salvage what I have.

 

Sorry, meant to show you coils. Here is how I mounted them. Can dig up part numbers if you need them.

 

Posted once and it's gone! On the '39 I had a company build a radiator to my specs. It was a drop in replacement for a '39 with LS mods. With these pre 40 fat fenders there is no room front to back AND side to side which is a receipt for ugly with all engine attachments. I like to use as much factory parts as possible in case a part goes south on a trip there is a replacement around the corner. My steam line goes into a sleeve on the upper radiator hose. When building my 33 ****** with an LT1 I put a fitting in the top tank and ran a braided brake hose to it for my steam line. I have read about steam pockets forming so I have elected to keep mine. Side note, the LS engine seems to be easy to cool.