According to Toro Rosso technical director Jody Egginton, the Honda engine's packaging is the "most complex" yet in the 2019 STR14.
The Red Bull Racing junior team enters its second season with its power being supplied by the Japanese manufacturer, with the Red Bull team also running with Honda this season.
Due to a late switch from Renault to Honda engines in 2017, the power unit for the side last season was not as progressed as it could have been with more time to work on it.
"Our chassis this year is probably the most complex we've done in terms of integrating it with the power unit. It's far more complex than last year's," Egginton told Motorsport.com.
"We've not been able to do that because we've become smart overnight but we've had the opportunity to work with the power unit supplier to optimise it all. And Red Bull have done the same as far as they're concerned.
"Honda is delivering an engine that to all intents and purposes is the same across the two teams. Red Bull seem happy and we're very happy with what we have got."
Egginto believes that the extra time they have now had to work alongside Honda has ensured the package will be a lot better.
"It's just a case of starting that design process earlier," Egginton said. "It can be something quite minor, a wastegate actuator positon. It's not a significant component but if you can think about it early enough and put it somewhere out the way where it suits everybody, it's not that something at the last minute you realise 'bugger, it's sitting out here'.
"With a customer power unit you get what you're given. The moment you start working with a supplier whose saying 'what do you want?' rather than saying 'how do we best use what we're given?'
"Last year with Honda we had some possibility to make some changes but not so many because the engine was confirmed late-2017. For this year, we've been able to ask some questions with Red Bull and Honda."