Need to replace a column value in UNIX file

Hi All,

I am having a file like below

01098546       3  56120610010377101008311121 001382    71    003         5011339
01099413       1  42120500010247081106112121 000304    46    002         2011339

I want to replace the 78 column from 3 to 4 and I need the file as below

01098546       3  56120610010377101008311121 001382    71    003         5011439
01099413       1  42120500010247081106112121 000304    46    002         2011439

Can you please help me in getting this done

Thanks,
Arun

---------- Post updated at 04:36 PM ---------- Previous update was at 04:25 PM ----------

Got my answer used the below command to make it done

 sed -i 's/339$/439/' file

If these are constant 80 character width records:

sed -e 's/3\(..\)$/4\1/'

If not:

awk 'BEGIN { FS = OFS = ""; } $(78) == "3" { $(78) = "4"; } { print; }'