MR HYDROSEED

Hi guys, before i bought this truck i was more of a car guy. i own a highly modified BMW M3 that i was planning on turbocharging. i learned everything i could about turbo's but never did any research about diesel engines and turbos. I thought i had everything figured out as to compressor maps, turbine housing sizes compressor wheels and sizes but in the Dodge diesel world it seems like nothing is like that. i'm lost, it's like i'm starting from scratch! I know everything about Garrett's T3, T3/T4 hybrids but when it comes to 12cm,14cm16cm i can't compare it to anything. Any help? i found some holset turbo's that i'm wondering if they might be compatable for a twin setup? also 2 cummins turbos. H1E, H2C and Cummins T46 and T50. Is there a difference between the Holset and a T4 garrett?