How to downgrade Rake

Hello and thanks in advance

I had/have a problem with engines and rake that throws the error:
undefined method `last' for {}:Hash
This is documented here:
http://railsforum.com/viewtopic.php?pid=50179

The fix is to downgrade Rake to version 7.3 (if you want to stay with
rails 1.2.3 or 1.2.5 which I need for substruct)

I found this set of instructions that are at the bottom of this page,
bit I think it is more for reinstalling gems 1.01 rather than just
downgrading Rake.

to downgrade Rake, can I just do this?
gem uninstall rake
gem install rake ver=0.7.3

I am guessing at the syntax. could someone please give me the correct
method(s)

Thanks in advance.

instructions for reinstalling gems 1.01
1.Uninstall the current rails - gem uninstall rails
2. Uninstall the current rake - gem uninstall rake (with out this
rails installation was throwing error)
3.clean up - gem clean
4.Down load the gems 1.0.1, unzip it
5.cd to the gems unziped folder
6.install new gem - ruby setup.rb
7. verify - gem -v , should report 1.0.1
8.clean up again - gem clean
9.Install rake - gem install rake , this will install rake 0.8.1
10.install rails - gem install rails thats it...it took some combos for
me to figure this out