Can i replace a 24/34/42 MTB chainset with a 24/38/48 MTB chainset while still using the same 7 speed cassett, chain and shifters.

My old mountain bike from the 90s had 24/38/48 MTB chainset and when i stood up and pedaled on flat roads i could get to 40mpg while now on my 2019 29er with 24/34/42 MTB chainset & 12-32 7 speed cassett i struggle to reach 30pmg while pedalling like crazy

EDITED: So it appears, i have a Formula DC22 rear hub, not sure if this help anyone to tell me if a 11-28 cassette will fit on it. Trek say i need to buy a whole new back wheel if i want to change the cassette. Here are some images of back wheel and cassette. [![enter image description here](https://i.stack.imgur.com/aHpHL.jpg)](https://i.stack.imgur.com/aHpHL.jpg)