Synchronized Tree speed

[MS66]

My truck is a '68 C-10 with a 250 and non synchronized 3 on the tree. I have a question about what 1st gear synchronized 3 speed gear box will be a direct swap. I want to keep everything the same(or very close to it) on the column shift linkage. Can someone steer me in the right direction where I might can find this information, my google powers aren't bringing any useful info yet. Thanks for any help.

FWIW, the 3 speed in my '69 G-10 van has synchronized 1st gear, it is spoiling me. Same engine as C-10.

EDIT: I found some useful info. My truck has a light duty Muncie 318 non synchro, seems the Saginaws are synched. Are all the Saginaw 3 speeds synchronized in first gear?
I need to rephrase my question, what all will I need to swap a Saginaw in place of the Muncie 318? Is it a feasible swap?

Found some more stuff. This is a pic off the internet of the transmission in my truck, Muncie SM318. OAL from bell housing to end of output shaft is 16.5".
Member 68gmsee on here did this exact swap long ago. He hasn't been on here since '22. Not a good sign. Hope all is well.

[bhap]

I swapped from a Muncie to a Saginaw OD three speed a few years ago. Depending on which Muncie you have - long or short - you may need to shorten your driveshaft. Mine was a longer Muncie and driveshaft would have fit, but needed a different front coupling to match the output shaft. It should bolt right in. Other than front of driveshaft, I had to lengthen one of my shift rods about 3”. My truck is a 62, but since yours is a 68, shift rods should be available in the junk yard. Good luck!