68 gmc short box rear gears
 

I use this forum sometimes because it's great to use when you are searching for info and useful knowledge from people who have been there and done that !! AS ALWAYS any help is greatly appreciated !!
I am currently working on a 68 GMC 1/2 ton short box I have taken the old 305 v6 out and replaced it with a 350 SBC with 450 hp I have kept the original SM24 4speed granny tranny in it with a 10" clutch and bell housing swap .. I now want to swap out the rear ring and pinion I know it's a dana 10 bolt rear and was wondering if any one would know what gear ratio came stock in there as I want to swap up to a higher gear ration so as not to crawl in 1st gear and get more out of 4th gear ... and any suggestions on the gear ration to use .....TY 4 any help...