i have a 95 2500 auto and it wont go into reverse. just wondering if i should rebuld the tranny or just go with a manual? the tranny has a few mods, i dont know whats been done to it but i have ground fuel plate few afc mods n shes holding. but i want to bump her up to round 500-600 horse. so what would be a better? upgraded auto or manual? and where to get a cheap one. thanks.