How would 'wanna' and 'gonna' be in the past simple?
I found examples on the Internet: 'I was gonna work' and 'I wannaed cake'
'Wanna', 'gonna', and 'was gonna' are commonly used reductions, (informal as teechar mentioned). I sometimes use them myself when speaking casually with friends.
I've never heard 'wannaed', however. Even when I'm using the reduced forms mentioned, I'd still use 'wanted' (or switch over to 'was gonna').
You'll hear similar reductions with certain modal verbs and the pronoun 'you'. For example, 'would you' becomes 'woudja', while 'could you' reduces to 'coudja'.
Yet another common one is reducing the 'of' in phrases like 'sort of' or 'kind of' to an 'a' - 'kinda, sorta'. Similarly 'ought to' can become 'outta'.
I usually do explain these to my students so they can recognize them if they hear them, but I don't encourage them to use them.
The country singer John Michael Montgomery used these reductions in a song. Since these reductions are typically a result of rapid speech, they lend themselves to fast-paced song. They also make for easy rhyming, as you can hear. You may also the so-called 'g-dropping' - omitting the 'g' sound on words ending in 'ing'.
https://www.youtube.com/watch?v=10hxo4F1ZyA&ab_channel=Naomi%E2%80%9CMacyferro2000%E2%80%9D
