Crank compatability
 

I have a Shimano 600 tricolored crank.I want to replace just the crank arm with a Shimano Biopace 105 that is longer.The 105 is fc-1050 series.Will it work?

Yep, will work fine. Replace both arms since it is longer. Rings, bolts, all will fit.

I've run both cranks, and am pretty sure I used a 110mm bottom bracket for both. So your chainline should be fine as well.
http://www.unc.edu/home/cupery/pics/...-600_crank.jpg
http://www.unc.edu/home/cupery/pics/..._105_crank.jpg

As rccardr noted, you can swap the chainrings between the two cranks as well, if you prefer to stick with round rings over the biopace rings.

The reason I'm doing this is my present crank is 170 and the other is 175.My seat is all the way back but my foot doesn't sit on the pedals with the ball of my feet comfy more towards the middle of the foot.I thought it will be better with the 175.Or do you guys think getting a seat post with a longer setback is better?

the sort of fit you are talking about should be covered by fore/aft adjustment of your saddle (and seatposts that can handle the proper amount of adjustment).
Crank length should be pretty much based on height - well technically on leg length (and a bit of variation for personal preference and pedaling style). How tall are you?

I'm 5'8".My seat is all the way back and I have a slight bendof the knees when I pedal,so I think the height is right.The bike is a pinarello Montello(1989)54cm.I don't understand why the fit is so awkward.

might be the, femur on your leg is long, but the setback, seat post offset ,
available from your current seat post, is too short, and the angle for the seat tube is too steep ..

Brand/model of frame is a mass production , the body of the rider is a variable..

the 5mm may be imperceptible, .. on its own..

i had a zero set back seat post , and a B 17 saddle, the combination of a saddle
with the ability, of a longer rail adjustment range, to shove it back, further ,
and a crank arm change from 170 to 180 gained an inch.

kept the seatpost, as it had a quality of suspension function

at your height, you don't need 175mm cranks. just get a seatpost that allows for more setback.

Where?Any suggestions that won't break the bank?

would want to see a picture (that you took, or search the model online) of your current post to have an idea of this first. If you currently have a zero-setback post, then probably any standard post that has some setback would be an improvement.
This is assuming you actually need more setback (instead of just raising the seatpost slightly), and you don't sound particularly knowledgeable, but that's your call.

live in person visit to the LBS is recommended , they can see you and the Bike fit issues.

concur

http://www.cyclesportsuk.co.uk/produ...3&currency=USD
This is the present seatpost.Normal setback.

would recommend you talk to someone who can judge your bike fit, in-person. Changing crankarm to something that's quite long for your height is not recommended, whatever the case.
if you want to get saddle moved back anyway, you could always get a downhill post.
http://bikeforums.net/attachment.php...hmentid=320558

Universal Cycles sells MANY seatposts, including the Velo Orange Grand Cru long setback post (27.2mm only), which is a very nice post especially for having a two bolt attachment, so easier for subtle seat angle adjustments.

http://www.universalcycles.com/shopp...p?category=167
http://www.universalcycles.com/shopp...&category=4309