I have just purchased a 94 blazer s 10 that has not been driven for about a year. It needed new ign distributor. Motor runs great now ,but the trans will only engage in reverse, it will not engage in drive?

Not good.
Have you checked fuse to transmission computer?
Any codes?
You may need to get it on a transmission capable scanner to check it out?
How is fluid level and filter and fluid condition?
Is the shift linkage good and tight and catching all gears?

what happens if you pull the gear selector down into 1st?

All the fuses are good. Fluid loks and smells good. No codes I do not have access to a trans scanner. Shift linkage is fine. When I put it in gear, there is a slight drop in rpm. If I shift down to 1st, I can feel minor torque build in the driveshaft and a slight reverse motion in the car? any thoughts

When I shift down to first, I can feel torque build in the driveshaft. I also get a slight drop in rpm, and it feels as if it tries to go in reverse

Not good.
Sounds like a clutch or sprag or planatary is locked up.
Get a transmission scanner and check things out first.
Also drop transmission oil pan and have a look in the bottom of pan.
Good luck
MT

If reverse engages without hesitation and firmly, and it drives in reverse, it is apparent that the low/reverse clutch is operating normally. There may be a problem with the forward (direct) clutch stack, forward sprag as MT described, or there still may be a problem with the valving, since the '94 models are among those "in between" years of ODB 1½ that don't always report errors to the driver as obviously as later years.

I've also seen some that have the direct clutch plates and steels so worn that the servo over-extends and cannot apply adequate pressure to lock the clutch:

http://mysite.verizon.net/strey/files/4L60OverRunForwardPistons.jpg

They were delaid due to Tropical storm fays flooding, but now have the trans codes #66 , #81 , #82. Any thoughts?

They are all 1-2 and 2-3 solenoid circuits fault codes?
Has it got good fuse and 12 V power to transmission computer and solenoids?
Check all wiring and power and grounds.
Check transmission wiring plugin.
Any transmission fluid in it.
Will it work and pull in manual low gear position?
Have you droped pan and have a look in there?