Heating（oil to gas) 取暖用燃油改烧天然气问题请教

Contractor 给出三个不同的报价：

Option 1:

1/ Carlin EZ Gas conversion natural gas burner connected to existing heating system and existing gas meter. Gas line will need to be increased from ¾” pipe to 1” pipe to accommodate for the new burner. 

Option 2:

1/ Peerless MI06 82% efficient natural gas boiler connected to existing gas meter, piping and venting. 

Option 3:

1/ Weil McLain Ultra PHD155 93% high efficiency natural gas boiler connected to existing gas meter and piping. 

我的理解第一个Option是只换burner和相应的piping，保留原先的existing heating system （boiler），有没有哪位做过，可行吗？ 谢谢!