You can make this T-5 swap work in your 46 without the adaptor or special bell housing, it's just more work. You'll just need to make some sort of bracket to mount the pedal assy to. I ended up with the adaptor because a friend offered to attempt to make one for me. It worked fine and the price was right. Another local buddy used the 1951 bell housing for his 41 pickup and it's fine. He had to do the usual mods the tech tips talk about re. the T-5, plus make an adaptor for his pedals. This T-5 is especially great in our early 40s trucks vs. the saginaw and other as the truck is so narrow.
About the electronic speedo, the folks I contacted with that very same question only offered to sell me an adaptor to my old speedo for about $300. Don't remember who I talked to, one of the major online speedo experts. So I found another trany with the old cable set up. You may want to post that question on the web site.
Sounds like your plan is similar to mine, leaning towards stock but want to make it all more livable. I'm planning the front disc job also, want 6 lug set up to keep my 15" artillery wheels.
Best of luck
