mm, still no luck.

RewriteRule completes/completes/(.*) /shop/completes/$1 [R=301,L]
RewriteRule /decks/decks/(.*) /shop/decks/$1 [R=301,L]
RewriteRule /wheels/wheels/(.*) /shop/wheels/$1 [R=301,L]
RewriteRule /trucks/trucks/(.*) /shop/trucks/$1 [R=301,L]
RewriteRule /bushings/bushings/(.*) /shop/bushings/$1 [R=301,L]
RewriteRule /safety-gear/safety-gear/(.*) /shop/safety-gear/$1 [R=301,L]
RewriteRule /accessories/accessories/(.*) /shop/accessories/$1 [R=301,L]
RewriteRule /sweet-deals/sweet-deals/(.*) /shop/sweet-deals/$1 [R=301,L]

Make sure that your rewrite rules are placed before the Joomla's SEF rules. If that doesn't help, try contacting your web host to help you configure your .htaccess file correctly or purchase 1 hour of our paid support at www.artio.net/e-shop/support-services/joomla-related-support-1h and we can check your .htaccess directly on your server.

For example, the following rule works fine on my test server:
RewriteRule completes/completes/(.*) /shop/completes/$1 [R=301,L]

great, that worked. did not realise i had to put it before the Joomla rules.