Possible to retrain muscle fibers?

I was listening to a podcast yesterday, I forget exactly which one it was as I listen for 8 hours a day at work, but I was introduced to the idea of 'retraining' muscles fibers.

To make a long story short, they said it was possible to retrain fast/slow twitch fibers to behave like the opposite with time. For example, doing timed sets or long negatives will encourage more of a slow twitch muscle growth and doing speed work with sub max will train fast.

I currently squat and deadlift in the 400's but notice when I move into snatch/clean my lifting numbers drop dramatically to 250 C/J and 185 snatch. I do attribute some of this to form.

My question is as follows: Assume I decide to focus on speed doing multiple sets of squats/dead at sub max 90% of the time, and only give 10% to maximal effort lifts, would it be possible to 'retrain' some slow twitch to become more explosive?

I get the idea behind speed work/max work every week a la westside which is pretty much a 50/50 split, but would it be advisable for a person who wanted to shift focus to Oly lifting to 'start over' and focus more and more on the speed aspect?

I think speed work, rep work, and max effort work are all needed to achieve maximal strength in any area of your training. If you were looking at training on speed work, you should not be anywhere near 90%, I'd say you need to be more along the 60-70% to achieve the explosiveness one looks for when training for speed. Max effort work for me is 80%,85%, 90-95%. The last week of my training cube will be the week where I go for PRs.

I know this may not really pertain to retraining muscle fibers, but I thought I'd throw in my 2 cents regarding speed and max effort work.

I have been training for speed and explosiveness for a little bit now and I am enjoying myself immensely for a couple reasons. First, in general, I'm faster at all of my other lifts. I think this is largely due to CNS adaptation. When you train the clean, or the snatch with the right weight, only a full commitment by your CNS will do. I found this new speed particularly useful dead lifting. It's almost as if there is a better mind/body connection. Consequently, when I train at my 90% of maximum, I pull more reps. So I am stronger at least in theory.
Secondly, recovery seems faster so I can train more which means progress has been better in terms of weekly volume. Of course that could be my own training belief that volume is king manifesting itself within my psyche.
Additionally, training at the higher volume and speed has the additional benefit of leaning me out which is my current goal.
In the end, I don't know if the fibers are being retrained or not, but I certainly feel that more fibers are getting the message: "Pull this F*cking weight off the ground!" ;-)