i have an 87 k-10 i just built a 350c.i. out of a short block i bought from a manufacturer, yet i feel a wicked power loss at ideal the motor is torque as hell and twist the truck in gear it doesnt have a lot of pep, is my 700r4 tranny bad or is it cuz im using a 3.73 rear with 35 in tires?

I don't know. Why not hold the keyboard up to the truck so I can see it better <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

Most likely it is the gearing/tire size. Look up some ring and pinion sites,get a phone number and call them. tell them what you are running and they will tell you the proper gears that you will need.
Also the 700r4 is a great tranny as long as it is 88 and newer,the older ones had a problem that they fixed in the newer ones.I think there is a kit that you can get that will fix that problem. Call up you local GM dealer and find out if there is a kit,if not see if you can trade in the older tranny for a newer one.Or call a tranny shop and see what your options are. personally i would go with the second choice,most dealers dont rebuild trannys anymore it is just a remove and replace.the trans shop will know more about what can be done to your trans to get the most from it.