Need some help with 350 TBI build

[Big_Bear84]

Hi,guys!
I've rebuilding my K5 and need some help.
I have 135k miles on it,all was fine,but i started a full rebuild. I've opened engine(after cold start was a little bit blue smoke behind car,so valve stem seals had to be replaced) and was thinking that i'll change only stem seals,but later i understood that i'd like to put new piston rings too.
So,i bought an Enginetech premium full engine rebuild kit and today started to put new parts.
I have changed valve stem seals,cam bearings,expansion plugs and started to put all in,but now i can't continue,because i have a small trouble with pistons and rings:
At first time i thought,that i'll change rings only,because stock pistons are fine with no problems,but new oil rings aren't same and i can't push piston to block. Then i was thinking about new pistons,which are also in rebuild kit ,but skirt of new piston is shorter than stock.
So,i have 2 ideas: put new pistons or put old oil rings with stock pistons... Compression rings are same like stock.
Which idea is better? What can be with motor if i'll put new short pistons?
P.S
New pistons are Enginetech P1505.
Condition of block is very good,still got hone in sylinders and i'll not bore them,so new pistons and rings are stock size.
Thanks alot,CK5'ers and greetings from Finland!

 

[78K30]

the TBI engines used two different oil ring groove depths. I found this out the hard way after the guy at the parts counter ordered the exact opposite set as to what I wanted.

I just took a caliper and measured the groove depth to confirm the measurement. Since you’re this far into it having the correct rings is the best way if you can wait to get them in the mail. Unless you feel like swapping pistons out which isn’t very hard either just time consuming.

 

[Big_Bear84]

the TBI engines used two different oil ring groove depths. I found this out the hard way after the guy at the parts counter ordered the exact opposite set as to what I wanted.

I just took a caliper and measured the groove depth to confirm the measurement. Since you’re this far into it having the correct rings is the best way if you can wait to get them in the mail. Unless you feel like swapping pistons out which isn’t very hard either just time consuming.

Thanks for the answer,James.
What problems can i have if skirt of new piston is shorter than stock? Noises,power loose or nothing?
It's not a problem to change pistons,but i'm not sure about skirt dimension..I'ts about 0.4" shorter than stock.