Will this engine/tranny combo work ok?

[Brad]

I'm getting ready to do the LWB-SWB swap and when I do, I think I'm going to swap out my 3 speed for a 4 speed NP435 and go back to 3.07 in the rearend. I've included my final drive calculations and gear reduction for the swap and want to know what you all think.

Here are the gear ratios for the SM-318 3-speed, the SM-420 and NP-435-GA 4-speed transmissions.
Trans 1st 2nd 3rd 4th Rev
SM-318 2.94:1 1.68:1 1.00:1 ~-~ 2.94:1
SM-420 7.06:1 3.58:1 1.71:1 1.00:1 6.78:1
NP-435-GA 4.56:1 2.28:1 1.31:1 1.00:1 5.64:1

- (my percentages don't seem to match up in this post, but you get the idea)

SM318 --- 10.97 6.27 3.73
\ / \ /
57% 59%

NP435 ---- 14.00 7.00 4.02 3.07
\ / \ / \ /
50% 57% 76%

Also, see this related post:
Will NP435 work with 1 piece driveshaft