What rear gear do I have?

[oneperfectrun]

Any of you guys or gals know what rear gear ratio I might have? The truck is a 1970 C10, half ton, originally inline 6 and powerglide. 12 bolt rear.

I have a 327 and 700r4 in it now. Trans has been in for a few years. The trans didn’t have a speedo gear on the shaft at install and I just got gears shipped in yesterday to get speedo going again. I put the gears in this afternoon and speedo is 9-10 mph slow according to gps.

The truck has P235/75R15 tires that measure right at 28” tall. With the ratio calculator I used I figured for 4.10 gears and came up with 15 tooth drive gear and 43 tooth driven gear.

SPID doesn’t give the ratio that I can tell. I just assumed gears were 4.10.

Anyone know what gears were common for the inline and powerglide?